Pdl1 peptides for use in cancer vaccines

ABSTRACT

The present invention relates to a PD-L1 peptide fragment, useful in cancer therapies as well as PD-L1 peptide fragments for use in a method for treatment or prevention of a cancer, when administered simultaneously or sequentially with an additional cancer therapy.

TECHNICAL FIELD

The present invention relates to novel PD-L1 peptide fragments, as well as compositions, uses, and kit-of-parts comprising these peptide fragments. Furthermore, the invention concerns PD-L1 peptide fragments for use in a method for treatment or prevention of a cancer, when administered simultaneously or sequentially with an additional cancer therapy.

BACKGROUND ART

The immune system has the capacity to recognize and destroy neoplastic cells; nevertheless, despite the fact that neoplastic transformation is associated with the expression of immunogenic antigens, the immune system often fails to respond effectively to these antigens. The immune system becomes tolerant towards these antigens. When this happens, the neoplastic cells proliferate uncontrollably leading to the formation of malignant cancers with poor prognosis for the affected individuals. The acquired state of tolerance must be overcome for cancer immunotherapy to succeed. Several lines of evidence suggest that T cells are the main effectors in the immunological response against cancer cell Immune regulatory proteins like indoleamine 2,3-dioxygenase (IDO), Cytotoxic T lymphocyte antigen 4 (CTLA-4) and Programmed cell death 1 ligand 1 (PD-L1) play a vital role in the immune suppression and tolerance induction of anti-cancer immune responses. CTLA-4 is a key negative regulator of T-cell responses, which can restrict the antitumor immune response. Recently, the anti-CTLA-4 antibody ipilimumab was approved by the FDA as well as EMEA for the treatment of melanoma after showing effect in clinical phase III studies. Another central mechanism counteracting tumor-specific immunity and preventing effective anticancer immunotherapy requires a specific environment in which tolerogenic dendritic cells (DC) play an essential role deviating the immune response away from effective immunity.

Programmed death-1 (PD1) is a regulatory surface molecule delivering inhibitory signals important to maintain T-cell functional silence against their cognate antigens. Its ligands, known as PD-L1 and PD-L2, or B7-H1 and B7-H2 are expressed on APCs, tumor cells, placental, and nonhematopoietic cells found in an inflammatory microenvironment. Interference with PD-1 or its ligand PD-L1 increases antitumor immunity. It appears that upregulation of PD-L1 is a mechanism that cancers can employ to evade the host immune system. Expression of PD-L1 on tumors correlates with poor clinical outcome for a number of cancers including pancreas, renal cell, ovarian, head and neck, and melanoma (Hamanishi et al., 2007, Proc. Natl. Acad. Sci. U. S. A. 104:3360-3365; Nomi et al., 2007, Clin. Cancer Res. 13:2151-2157; Hino et al., 2010, Cancer. 116:1757-1766. Thus, analysis of 196 tumor specimens from patients with renal cell carcinoma found that high tumor expression of PD-L1 was associated with increased tumor aggressiveness and a 4.5-fold increased risk of death (Thompson et al., 2004, Proc. Natl. Acad. Sci. U. S. A. 101:17174-17179). Ovarian cancer patients with higher expression of PD-L1 had a significantly poorer prognosis than those with lower expression of PD-L1. An inverse correlation was observed between PD-L1 expression and intraepithelial CD8+ T-lymphocyte count, suggesting that PD-L1 on tumor cells may suppress antitumor CD8+ T cells (Hamanishi et al., 2007, vide supra).

Dendritic cells (DCs) are the most potent antigen-presenting cells, and they have been shown to effectively stimulate specific immune responses.¹ DC vaccines are generally composed of peripheral blood monocytes that are matured into DCs and pulsed with antigens in vitro before they are injected. DC-based cancer vaccines have received much attention over the last decade. However, although many DC vaccination trials have been conducted, clinical benefit has been limited for the majority of patients. With current vaccination strategies, the induced T cell frequencies are not impressive and additional measures are needed to help increase T cell response. Thus, further research is required to optimize the generation and phenotype of DCs to enhance their capacity to induce “fully armored” T cells, to determine the best route of administration, and to identify ideal combinations with additional therapies.

Programmed death 1 (PD-1) is an inhibitory molecule that is expressed on the surface of T cells. The PD-1 ligand PD-L1 (also known as CD274 or B7-H1) is constitutively expressed on lymphoid cells such as monocytes, DCs, and T cells, and it is also present on nonhematopoietic cells, such as endothelial and epithelial cells.^(2,3) PD-L1 can be upregulated by type I and II interferons (IFNs) through IFN regulatory factor-1 (IRF-1) in what appears to be a JAK/STAT-dependent manner.⁴ In general, interactions between PD-1 on T cells and PD-L1 control the induction and maintenance of peripheral cell tolerance during normal immune responses.⁵ PD-L1 is a critical negative regulator of self-reactive T cells during both the induction and effector phases of autoimmune disease, and it exerts its inhibitory function in multiple ways. In addition to being a ligand for PD-1, PD-L1 binds B7-1 (CD80), preventing B7-1 co-stimulation. IL-10 is produced upon ligation of PD-L1 and possibly augments apoptosis of activated T cells.⁶ The immune system is continually looking for foreign pathogens and irregular cells, such as cancer cells. Consequently, in order for cancer to continue to grow, it must hide from the immune system to avoid destruction. PD-1 and its ligands play a central role in maintaining peripheral tolerance and preventing autoimmunity, and cancer cells can exploit this system to create a suppressing microenvironment, thus protecting themselves from immune-mediated killing. Indeed, PD-L1 expression has been found to be high in multiple cancers,^(7,8) and PD-L1 expression was first described as an indicator of tumor aggressiveness in renal cell carcinoma.⁹ In addition, PD-L1 expression on tumor cells has been suggested as a prognostic factor in a number of solid cancers, including ovarian and pancreatic cancer. 10,11

Blockade of either PD-1 or PD-L1 by monoclonal antibodies has resulted in outstanding clinical responses,^(12,13) and the anti-PD1 antibodies pembrolizumab and nivolumab were recently approved for the treatment of metastatic melanoma by the United States Food and Drug Administration (FDA) (September and December 2014, respectively). The recent discovery of PD-L1-specific T cells suggests that the immune system itself has a mechanism to counteract the effects of PD-1 and its ligand.^(14,15) Indeed, PD-L1-specific T cell responses in peripheral blood were shown to occur at higher frequencies in cancer patients than in healthy donors. 14,15 Subsequently, these PD-L1-specific T cells were found to lyse PD-L1-expressing cells, including melanoma cells and nonmalignant DCs.^(14,16) In addition, activation of PD-L1-specific T cells boosts the immune response toward viral antigens.¹⁷ These findings suggest an autoreactive function for PD-L1-specific T cells in immune homeostasis. Furthermore, it implies that stimulation with PD-L1-derived peptides can boost a previously existing or vaccine-generated immune response by pushing the immune balance in the microenvironment toward less immune inhibition.

We recently conducted a vaccine study in patients with stage IV malignant melanoma (Borch et al., in preparation). In the study, patients were vaccinated with DCs transfected with mRNA encoding the tumor-associated antigens p53, survivin and telomerase (the vaccine is referred to herein as “DCvacc”). However, the clinical benefits were limited and immunological monitoring of the patients revealed that their peripheral blood mononuclear cells (PBMCs) had only limited reactivity toward DCvacc.

SUMMARY OF THE INVENTION

The present inventors have identified new fragments of human PD-L1 (SEQ ID NO:1) which fragments have good solubility, do not aggregate, are not prone for beta-sheet formation and as such are suitable for, for instance, vaccines together with an adjuvant. The PD-L1 peptide fragment of SEQ ID NO. 91 (which is PDlong2 described in WO2013056716, incorporated herein by reference) is quite hydrophobic and very prone for beta-sheet formation and therefore has low solubility. Furthermore, this peptide contains free SH, and must be handled at low pH to prevent dimer formation.

Furthermore, it has been shown (see below) that the PD-L1 peptide fragments SEQ ID NO. 91 and 89 (referred to in WO2013056716 and herein as PDlong2 and PDlong1 respectively) co-stimulation increases immunogenicity of a dendritic cell-based cancer vaccine. Thus, activation of PD-L1-specific T cells by any one of these two PD-L1 peptide fragments may directly modulate immunogenicity of DC vaccines. Addition of PD-L1 epitopes may thus be an easily applicable and attractive option to augment the effectiveness of cancer vaccines and other immunotherapeutic agents. Thus, it is contemplated that a PD-L1 peptide fragment consisting of SEQ ID NO. 91 or a PD-L1 peptide fragment consisting of SEQ ID NO. 89, as well as longer sequences comprising these will have the effect as shown herein.

In one aspect the present invention relates to a PD-L1 peptide fragment, or pharmaceutically acceptable sale thereof, having the formula:

X¹VILGAILLCLGVALTFIX² (SEQ ID NO: 78) wherein

-   N-terminal X¹ is selected from a group consisting of L, HL, THL,     RTHL (SEQ ID NO: 79), -   ERTHL (SEQ ID NO: 80), NERTHL (SEQ ID NO: 81), or is absent, -   C-terminal X² is selected from a group consisting of F, FR, FRL,     FRLR (SEQ ID NO: 82), -   FRLRK (SEQ ID NO: 83), FRLRKG (SEQ ID NO: 84), FRLRKGR (SEQ ID NO:     85), -   FRLRKGRM (SEQ ID NO: 86), FRLRKGRMM (SEQ ID NO: 87), FRLRKGRMMD (SEQ     ID NO: 88), or is absent, -   provided that if X1 is absent, then X2 is not FRLRKG (SEQ ID NO:     84), -   wherein the C-terminal amino acid also comprises the amide. In other     words, the C terminal amino acid may be replaced with its     corresponding amide. X¹ and X² may each be independently selected     from the available options.

Where the amino acid form of the C terminal residue is present, this may be indicated herein by the notation X—OH, whereas if the amide form is present this may be indicated by the notation X—NH₂. If neither notation is used, it will be understood that both amino acid and amide forms of the C terminal residue are encompassed. The peptide of the invention, or the pharmaceutically acceptable salt thereof, may therefore comprise or consist of any one of the amino acid sequences set out in Table A, optionally wherein the C terminal amino acid is replaced with the corresponding amide form.

TABLE A SEQ Peptide ID Start End name No Sequence pos pos  2 VILGAILLCLGVALTFI 242 258  3 VILGAILLCLGVALTFIF 242 259  4 VILGAILLCLGVALTFIFR 242 260  5 VILGAILLCLGVALTFIFRL 242 261  6 VILGAILLCLGVALTFIFRLR 242 262  7 VILGAILLCLGVALTFIFRLRK 242 263  8 VILGAILLCLGVALTFIFRLRKGR 242 265  9 VILGAILLCLGVALTFIFRLRKGRM 242 266 10 VILGAILLCLGVALTFIFRLRKGRMM 242 267 11 VILGAILLCLGVALTFIFRLRKGRMMD 242 268 12 LVILGAILLCLGVALTFI 241 258 13 LVILGAILLCLGVALTFIF 241 259 14 LVILGAILLCLGVALTFIFR 241 260 15 LVILGAILLCLGVALTFIFRL 241 261 16 LVILGAILLCLGVALTFIFRLR 241 262 17 LVILGAILLCLGVALTFIFRLRK 241 263 18 LVILGAILLCLGVALTFIFRLRKG 241 264 19 LVILGAILLCLGVALTFIFRLRKGR 241 265 20 LVILGAILLCLGVALTFIFRLRKGRM 241 266 21 LVILGAILLCLGVALTFIFRLRKGRMM 241 267 22 LVILGAILLCLGVALTFIFRLRKGRMMD 241 268 23 HLVILGAILLCLGVALTFI 240 258 24 HLVILGAILLCLGVALTFIF 240 259 25 HLVILGAILLCLGVALTFIFR 240 260 26 HLVILGAILLCLGVALTFIFRL 240 261 27 HLVILGAILLCLGVALTFIFRLR 240 262 28 HLVILGAILLCLGVALTFIFRLRK 240 263 29 HLVILGAILLCLGVALTFIFRLRKG 240 264 30 HLVILGAILLCLGVALTFIFRLRKGR 240 265 31 HLVILGAILLCLGVALTFIFRLRKGRM 240 266 32 HLVILGAILLCLGVALTFIFRLRKGRMM 240 267 33 HLVILGAILLCLGVALTFIFRLRKGRMM 240 268 D 34 THLVILGAILLCLGVALTFI 239 258 35 THLVILGAILLCLGVALTFIF 239 259 36 THLVILGAILLCLGVALTFIFR 239 260 37 THLVILGAILLCLGVALTFIFRL 239 261 38 THLVILGAILLCLGVALTFIFRLR 239 262 39 THLVILGAILLCLGVALTFIFRLRK 239 263 40 THLVILGAILLCLGVALTFIFRLRKG 239 264 41 THLVILGAILLCLGVALTFIFRLRKGR 239 265 42 THLVILGAILLCLGVALTFIFRLRKGRM 239 266 43 THLVILGAILLCLGVALTFIFRLRKGRM 239 267 M 44 THLVILGAILLCLGVALTFIFRLRKGRM 239 268 MD 45 RTHLVILGAILLCLGVALTFI 238 258 46 RTHLVILGAILLCLGVALTFIF 238 259 47 RTHLVILGAILLCLGVALTFIFR 238 260 48 RTHLVILGAILLCLGVALTFIFRL 238 261 49 RTHLVILGAILLCLGVALTFIFRLR 238 262 50 RTHLVILGAILLCLGVALTFIFRLRK 238 263 51 RTHLVILGAILLCLGVALTFIFRLRKG 238 264 IO104.1 52 RTHLVILGAILLCLGVALTFIFRLRKGR 238 265 53 RTHLVILGAILLCLGVALTFIFRLRKGR 238 266 M 54 RTHLVILGAILLCLGVALTFIFRLRKGR 238 267 MM 55 RTHLVILGAILLCLGVALTFIFRLRKGR 238 268 MMD 56 ERTHLVILGAILLCLGVALTFI 237 258 57 ERTHLVILGAILLCLGVALTFIF 237 259 58 ERTHLVILGAILLCLGVALTFIFR 237 260 59 ERTHLVILGAILLCLGVALTFIFRL 237 261 60 ERTHLVILGAILLCLGVALTFIFRLR 237 262 61 ERTHLVILGAILLCLGVALTFIFRLRK 237 263 62 ERTHLVILGAILLCLGVALTFIFRLRKG 237 264 63 ERTHLVILGAILLCLGVALTFIFRLRKG 237 265 R 64 ERTHLVILGAILLCLGVALTFIFRLRKG 237 266 RM 65 ERTHLVILGAILLCLGVALTFIFRLRKG 237 267 RMM 66 ERTHLVILGAILLCLGVALTFIFRLRKG 237 268 RMMD 67 NERTHLVILGAILLCLGVALTFI 236 258 68 NERTHLVILGAILLCLGVALTFIF 236 259 69 NERTHLVILGAILLCLGVALTFIFR 236 260 70 NERTHLVILGAILLCLGVALTFIFRL 236 261 71 NERTHLVILGAILLCLGVALTFIFRLR 236 262 72 NERTHLVILGAILLCLGVALTFIFRLRK 236 263 73 NERTHLVILGAILLCLGVALTFIFRLRK 236 264 G 74 NERTHLVILGAILLCLGVALTFIFRLRK 236 265 GR 75 NERTHLVILGAILLCLGVALTFIFRLRK 236 266 GRM 76 NERTHLVILGAILLCLGVALTFIFRLRK 236 267 GRMM 77 NERTHLVILGAILLCLGVALTFIFRLRK 236 268 GRMMD

The “Start pos” and “End pos” columns indicate the starting position and the ending position of each peptide within the sequence of SEQ ID NO: 1. As will be appreciated from the table, the peptides of the invention comprise or consists of between 17 and 33 consecutive amino acids of the PD-L1 sequence of SEQ ID NO: 1. As described herein, additional residues may be added at the N and/or C termini to improve stability. The consecutive amino acids of SEQ ID NO: 1 preferably comprise at least the amino acids corresponding to positions 242 to 258 of SEQ ID NO: 1, with upto 10 additional amino acids at the C terminal end corresponding to positions 259 to 268 of SEQ ID NO: 1; and/or upto 6 additional amino acids at the N terminal end corresponding to positions 236 to 241 of SEQ ID NO: 1. Particularly preferred is the peptide which comprises or consists of the amino acid sequence RTHLVILGAILLCLGVALTFIFRLRKGR (SEQ ID NO: 52), which corresponds to positions 238 to 265 of SEQ ID NO: 1. This peptide may be referred to herein as IO104.1. The C terminal residue of this sequence may be replaced with the corresponding amide form and be equally preferred. The fragment with C terminal amino acid may be referred to as IO104.1-OH. The fragment with C terminal amide may be referred to herein as IO104.1-NH₂. One, two, three, four or five conservative substitutions may be made to any one of the sequences of Table A and the resulting sequence still be considered a peptide of the invention, although said peptide is preferably capable of recognition by T cells specific for the HLA-A2 epitope entitled PDL111 (sequence provided as SEQ NO: 92). Most preferably, said conservative substitutions do not alter the amino acids corresponding to positions 250 to 258 of SEQ ID NO: 1, which are the amino acid sequence of the PDL111 epitope.

In one embodiment the peptide fragment of the present invention is selected from

-   NERTHLVILGAILLCLGVALTFIFRLRKGRMMD (SEQ ID NO: 77), -   NERTHLVILGAILLCLGVALTFIFRLRKGRMMD-NH₂ (SEQ ID NO: 77 with C terminal     amide), -   RTHLVILGAILLCLGVALTFIFRLRKGR (SEQ ID NO: 52), -   RTHLVILGAILLCLGVALTFIFRLRKGR-NH₂ (SEQ ID NO: 52 with C terminal     amide), -   NERTHLVILGAILLCLGVALTFI (SEQ ID NO: 67) -   NERTHLVILGAILLCLGVALTFI-NH₂ (SEQ ID NO: 67 with C terminal amide), -   VILGAILLCLGVALTFI (SEQ ID NO: 2), -   VILGAILLCLGVALTFI-NH₂ (SEQ ID NO: 2 with C terminal amide), or a     pharmaceutically acceptable salt thereof. Typically, the peptide     fragment is selected from -   NERTHLVILGAILLCLGVALTFIFRLRKGRMMD (SEQ ID NO: 77), -   RTHLVILGAILLCLGVALTFIFRLRKGR (SEQ ID NO: 52), and -   RTHLVILGAILLCLGVALTFIFRLRKGR-NH₂ (SEQ ID NO: 52 with C terminal     amide).

In a further aspect the present invention relates to a composition comprising the PD-L1 peptide fragment of the present invention; optionally together with a pharmaceutically acceptable additive.

In a still further aspect the present invention relates to an immunotherapeutic composition, such as a vaccine, comprising

-   a) the PD-L1 peptide fragment of the present invention; and -   b) an adjuvant; -   for use as a medicament.

In an embodiment the immunotherapeutic composition of the present invention is for use in a method for treatment or prevention of a disease, disorder or condition selected from cancer, such as a tumor forming cancer disease; an infection, such as an infectious disease, e.g. an intracellular infection, for example an intracellular infection with a pathogen selected from the group consisting of L. monocytogenes and plasmodium, a viral infection, for example an infection with a virus selected from the group consisting of HIV and hepatitis; an autoimmune disease, such as diabetes, SLE and sclerosis.

In a further embodiment the adjuvant is selected from the group consisting of bacterial DNA based adjuvants, oil/surfactant based adjuvants, viral dsRNA based adjuvants, imidazochinilines, a Montanide ISA adjuvant.

In a further aspect the present invention relates to a kit-of-parts comprising:

-   a) the immunotherapeutic composition of the present invention, and -   b) a composition comprising at least one second active ingredient,     selected from an immunostimulating compound, such as an interleukin,     e.g. IL-2 and or IL-21, an anti-cancer agent, such as a     chemotherapeutic agent, e.g. Actimide, Azacitidine, Azathioprine,     Bleomycin, Carboplatin, Capecitabine, Cisplatin, Chlorambucil,     Cyclophosphamide, Cytarabine, Daunorubicin, Docetaxel,     Doxifluridine, Doxorubicin, Epirubicin, Etoposide, Fludarabine,     Fluorouracil, Gemcitabine, Hydroxyurea, Idarubicin, Irinotecan,     Lenalidomide, Leucovorin, Mechlorethamine, Melphalan,     Mercaptopurine, Methotrexate, Mitoxantrone, nivolumab, Oxaliplatin,     Paclitaxel, pembrolizumab, Pemetrexed, Revlimid, Temozolomide,     Teniposide, Thioguanine, Valrubicin, Vinblastine, Vincristine,     Vindesine and Vinorelbine. In an embodiment the provided     compositions are to be administered simultaneously or sequentially.

In a still further aspect the present invention relates to a method of treating a clinical condition characterized by expression of PD-L1, the method comprising administering to an individual suffering from said clinical condition an effective amount of the peptide fragment of the present invention, the composition of the present invention, or the kit-of-parts of the present invention.

In a further aspect the present invention relates to use of a peptide fragment of the present invention for the manufacture of a medicament, such as an immunotherapeutic composition or vaccine, for the treatment or prevention of a clinical condition characterized by expression of PD-L1. In one embodiment the clinical condition to be treated is a cancer disease where PD-L1 is expressed. In another embodiment the clinical condition is selected from the group consisting of infectious diseases and autoimmune diseases.

In a still further aspect the present invention relates to a PD-L1 peptide fragment having the formula:

X¹VILGAILLCLGVALTFIX² wherein

-   N-terminal X¹ is selected from a group consisting of L, HL, THL,     RTHL (SEQ ID NO: 79), -   ERTHL (SEQ ID NO: 80), NERTHL (SEQ ID NO: 81), or is absent, -   C-terminal X² is selected from a group consisting of F, FR, FRL,     FRLR (SEQ ID NO: 82), -   FRLRK (SEQ ID NO: 83), FRLRKG (SEQ ID NO: 84), FRLRKGR (SEQ ID NO:     85), -   FRLRKGRM (SEQ ID NO: 86), FRLRKGRMM (SEQ ID NO: 87), FRLRKGRMMD (SEQ     ID NO: 88), or is absent, -   provided that if X1 is absent, then X2 is not FRLRKG (SEQ ID NO:     84), -   wherein the C-terminal amino acid also comprises the amide, or -   a pharmaceutically acceptable salt thereof;

for use in a method for treatment or prevention of a cancer, when administered simultaneously or sequentially with an additional cancer therapy, such as a cytokine therapy, a T-cell therapy, an NK therapy, an immune system checkpoint inhibitor, chemotherapy, radiotherapy, immunostimulating substances, gene therapy, antibodies and dendritic cells. The PD-L1 peptide fragment may be selected from any of those disclosed in Table A, or a pharmaceutically acceptable salt thereof, optionally wherein the C terminal amino acid is replaced with the corresponding amide form. In an embodiment the PD-L1 peptide fragment is selected from

-   NERTHLVILGAILLCLGVALTFIFRLRKGRMMD (SEQ ID NO: 77), -   NERTHLVILGAILLCLGVALTFIFRLRKGRMMD-NH₂ (SEQ ID NO: 77 with C terminal     amide), -   RTHLVILGAILLCLGVALTFIFRLRKGR (SEQ ID NO: 52), -   RTHLVILGAILLCLGVALTFIFRLRKGR-NH₂ (SEQ ID NO: 52 with C terminal     amide), -   NERTHLVILGAILLCLGVALTFI (SEQ ID NO: 67), -   NERTHLVILGAILLCLGVALTFI-NH₂ (SEQ ID NO: 67 with C terminal amide), -   VILGAILLCLGVALTFI (SEQ ID NO: 2), -   VILGAILLCLGVALTFI-NH₂ (SEQ ID NO: 2 with C terminal amide), or -   a pharmaceutically acceptable salt thereof. Typically, the peptide     fragment is selected from -   NERTHLVILGAILLCLGVALTFIFRLRKGRMMD (SEQ ID NO: 77), -   RTHLVILGAILLCLGVALTFIFRLRKGR (SEQ ID NO: 52), and -   RTHLVILGAILLCLGVALTFIFRLRKGR-NH₂ (SEQ ID NO: 52 with C terminal     amide).

In a further aspect the present invention relates to a PD-L1 peptide fragment comprising the formula:

FMTYWHLLNAFTVTVPKDL (SEQ ID NO: 89) wherein the C-terminal amino acid also comprises the amide, or a pharmaceutically acceptable salt thereof;

for use in a method for treatment or prevention of a cancer, when administered simultaneously or sequentially with an additional cancer therapy, such as a cytokine therapy, a T-cell therapy, an NK therapy, an immune system checkpoint inhibitor, chemotherapy, radiotherapy, immunostimulating substances, gene therapy, antibodies and dendritic cells. In an embodiment the PD-L1 peptide fragment is selected from the PD-L1 fragment having the formula: FMTYWHLLNAFTVTVPKDL (SEQ ID NO: 89) wherein the C-terminal amino acid also comprises the amide. In a further embodiment the additional cancer therapy is selected from an immune system checkpoint inhibitor, wherein the inhibitor is a checkpoint blocking antibody selected from Actimide, Azacitidine, Azathioprine, Bleomycin, Carboplatin, Capecitabine, Cisplatin, Chlorambucil, Cyclophosphamide, Cytarabine, Daunorubicin, Docetaxel, Doxifluridine, Doxorubicin, Epirubicin, Etoposide, Fludarabine, Fluorouracil, Gemcitabine, Hydroxyurea, Idarubicin, Irinotecan, Lenalidomide, Leucovorin, Mechlorethamine, Melphalan, Mercaptopurine, Methotrexate, Mitoxantrone, Nivolumab, Oxaliplatin, Paclitaxel, Pembrolizumab, Pemetrexed, Revlimid, Temozolomide, Teniposide, Thioguanine, Valrubicin, Vinblastine, Vincristine, Vindesine and Vinorelbine.

DESCRIPTION OF DRAWINGS

FIG. 1. Costimulation with PD-L1-derived epitopes enhance the frequency of T cells reactive against dendritic cell vaccine. (A) PBMCs (5×10⁶) from patients were stimulated twice in vitro with DCvacc. The following day, the cultures were costimulated with one or two long PD-L1 epitopes or incubated with an irrelevant HIV control peptide. All cultures were stimulated with IL2 the day after peptide stimulation. Cultures were examined for DCvacc-reactive T cells after 16-20 days by intracellular TNFα/INFγ staining. (B-E) Examples of PBMC cultures from three melanoma patients in which co-activation of PD-L1 specific T cells significantly boosted T cell immunity toward DCvacc, as measured by intracellular TNFα/INFγ staining. (B) CD4⁺ T cells released only TNFα in response to DCvacc. (C) PD-L1 peptide costimulation induced TNFα/INFγ double-positive CD4⁺ T cells in response to DCvacc. (D, E) Costimulation with PD-L1 epitopes increased the number of both CD4⁺ and CD8⁺ cells that reacted against DCvacc.

FIG. 2. Costimulation of PBMCs with PDLong1 plus dendritic cell vaccine. At days 16-20, after two stimulations with DCvacc and two stimulations with either an irrelevant control peptide or PDLong1 peptide, the percentage of cells that released TNFα/INFγ in response to DCvacc was identified by flow cytometry. Percentages of DCvacc-reactive CD4⁺ T cells (A) and CD8⁺ T cells (B) in cultures of PBMCs taken from eight melanoma patients before vaccination (baseline) and after four vaccinations.

FIG. 3. Natural T cell responses to PDLong1 and PDLong2. (A) IFNγ ELISPOT was used to measure T cell response towards PDLong1 and PDLong2 in tumor-infiltrating lymphocytes from melanoma patients. In 5×10⁴ cells from 12 melanoma patients, the average number of IFNα-releasing cells in response to either PDLong1 or PDLong2 was measured. (B) Example of ELISPOT wells performed with TILs from two melanoma patients either without or with PDLong1 or PDLong2 peptides (C) Tumor-infiltrating lymphocytes were cultured for 5 hours either without or with PDLong1 or PDLong2 before being analyzed for intracellular IFNγ/TNFα staining. (D) Example of IFNγ/TNFα staining of tumor-infiltrating lymphocytes from a melanoma patient in response to either without peptide or with PDLong1 or PDLong2.

FIG. 4. Stimulation of patient PBMCs with PDLong1 plus PDLong2 together with a DC vaccine. At days 16-20, after two stimulations with DCvacc and two stimulations with either an irrelevant control peptide or PDLong1 plus PDLong2 peptide, the percentage of cells that released TNFα/INFγ in response to DCvacc was identified by flow cytometry. Percentages of DCvacc-reactive CD4⁺ T cells (A) and CD8⁺ T cells (B) in cultures of PBMCs taken from eight melanoma patients before vaccination (baseline) and after four vaccinations.

FIG. 5. Comparison of cytokine secretion in supernatants from cultures of cells from four patients. Supernatants from cultures either costimulated with an irrelevant control peptide or with PDLong1 plus PDLong2 were collected on the day of analysis of DCvacc-reactive T cells so that the presence of IFNγ (A), IL-6 (B), or TFGβ(C) could be measured. (D) In addition, the total numbers of cells were counted after the second stimulation with either HIV or PDLong1 plus PDLong2 epitopes.

FIG. 6. Measurement of IFNγ releasing cells in tumor infiltrating lymphocytes of melanoma patients in response to IO104.1-OH and IO104.1-NH₂ versus an irrelevant control peptide

FIG. 7. ELISPOT comparison of PDL111-specific CD8-T cell responses to PDLong2, IO104.1-OH, IO104.1-NH₂. PDL111 and an irrelevant control peptide.

FIG. 8. T cells specific for murine PDL1 are naturally occurring in mice. A) shows the timeline for the experiment described in Example 3; B) Elispot results for splenocytes stimulated with one of 5 peptide candidates ex vivo; C) Representative Elispot wells and results for splenocytes stimulated with the most effective peptide (mLong1). n=5-10 mice/group.

FIG. 9. Local inflammation caused by the allergen 2,4-dinitrofluorobenzene (DNFB) elicits a PD-L1-specific T cell response in mice. A) shows the timeline for the experiment described in Example 4; B) Elispot results for cells from the spleen and dLNs was stimulated with mPD-L1long1 or mPD-L1short ex vivo; C) Representative Elispot wells of one of the DNFB treated mice with highest response compared to a control. n=12 mice/group

FIG. 10. Vaccination with mPD-L1long1 expands the population of PD-L1-specific T cells in mice. A) shows the timeline for the experiment described in Example 5; B) Elispot results for splenocytes stimulated with mPD-L1long1 or mPD-L1short ex vivo; C) Elispot wells of a representative mouse from each group. n=3-4 mice/group.

FIG. 11. Vaccination with mPD-L1long1 shows anti-tumor effect in mice. A) shows the timeline for the experiment described in Example 6; B) Change in tumor volume over time for each mouse (M1-M3 vaccinated with Montanide only; M4-M5 vaccinated with mPD-L1long1 plus Montanide); C) Kaplan-Meier survival curve; D) Change in mean tumor volume over time for each group. n=3 mice/group.

DESCRIPTION OF SEQUENCES

SEQ ID NO: 1 is the full length amino acid sequence of human (h)PD-L1

SEQ ID NOs: 2 to 77 are the amino acid sequences of exemplary peptides of the invention, all of which are fragments of hPD-L1.

SEQ ID NO: 78 is an amino acid sequence representing a general formula corresponding to the peptides of the invention.

SEQ ID NOs: 79 to 81 are various N terminal amino acid sequences which may be added to the formula of SEQ ID NO: 78.

SEQ ID NOs: 82 to 88 are various C terminal amino acid sequences which may be added to the formula of SEQ ID NO: 78.

SEQ ID NO: 89 is another exemplary peptide of the invention, being a fragment of hPD-L1

SEQ ID NO: 90 is a T cell epitope sequence comprised within SEQ ID NO: 89.

SEQ ID NO: 91 is the amino acid sequence of a fragment of hPDL1 which is disclosed herein

SEQ ID NO: 92 is the amino acid sequence of the HLA-A2 epitope entitled PDL111 (corresponds to positions 250-258 of hPDL1),

_(SEQ)ID NOs: 93 and 94 are the amino acid sequence of certain peptides used as controls in the Examples.

SEQ ID NO: 95 is the full length amino acid sequence of murine (m)PD-L1.

SEQ ID NOs: 96 to 100 are the amino acid sequences of peptides derived from mPD-L1 which are used as analogs for the peptides of the invention in the mouse model experiments described in the Examples.

SEQ ID NO: 101 is a T cell epitope sequence comprised within SEQ ID NO: 96.

DETAILED DESCRIPTION OF THE INVENTION

The problem of cancer immunosuppression was solved in WO2013056716 wherein PD-L1 fragments of human PD-L1 full length (SEQ ID NO. 1) was based on the surprising finding by the inventors of spontaneous cytotoxic immune responses against PD-L1 expressing cells in cancer patients. These findings open the way for novel therapeutic and diagnostic approaches which may be generally applicable in the control of cancer diseases. Interestingly, the findings are not restricted to cancer but are also useful in other clinical conditions characterized by the presence of undesired cells expressing PD-L1.

The invention disclosed in WO2013056716 targets the cancer disease by killing the PD-L1 expressing cancer cells directly and by killing the PD-L1 expressing regulatory cells. This is done by enabling the T cells to recognize the PD-L1 expressing cells. Likewise, when the clinical condition is an infection, T cells are enabled to kill PD-L1 expressing APCs /DCs. Thus, the expression of the immune suppressing enzyme PD-L1 in cancer cells and APCs is positive in conjunction with the application of the method of the present invention, which targets these PD-L1 expressing cells. This approach, especially as it entails the killing of the APCs/DCs, goes against the common opinion in the field, where PD-L1 generally is attempted inhibited in order to remove the tolerating milieu around the APCs/DCs while preserving these cells, which are considered required in order to launch an effective immune response. Furthermore, the finding of spontaneous cytotoxic immune responses against PD-L1 expressing cells is particularly surprising since PD-L1 expressing cells antagonize the desired effects of other immunotherapeutic approaches. Therefore, a combination of PD-L1- and tumor-targeting immunotherapies is highly synergistic. The presence of an in vivo T-cell response specific for PD-L1 demonstrates that cancer patients are capable of generating T-cell responses to PD-L1 in vivo in response to the presence of PD-L1 peptides. Thus, the two conditions for generating a T-cell response are met: The T cells are present in the cancer patient and they have the ability to expand, which are shown in the application as filed. It follows from the general knowledge in the field of immunology that providing additional PD-L1 protein or PD-L1 peptides will lead to generation of PD-L1 specific T-cell responses. In contrast to membrane-bound antibodies on B cells, which can recognize antigen alone, the T-cells recognizes a complex ligand, comprising an antigenic peptide bound to a protein called the major histocompatibility complex (MHC). In man, this molecule is known as human leukocyte antigen (HLA). Class I HLA molecules sample peptides from protein-degradation inside the cell and present these at the cell surface to T cells. Hence, this enables T-cells to scan for cellular alterations. When a T cell encounters antigen in the context of a HLA molecule, it undergoes clonal expansion and differentiates into memory and various effector T cells. Hence, identification of a spontaneous immune response is evidence that an antigen is a T-cell target. It demonstrates that specific T-cells have already been activated and have expanded in vivo.

The PD-L1 peptide fragment of SEQ ID NO.91 (described in WO2013056716 as PDLong2) is quite hydrophobic and very prone for beta-sheet formation and therefore has low solubility. Furthermore, this peptide contains free SH, and must be handled at low pH to prevent dimer formation. Hence, there is a need for a more soluble and easy to handle PD-L1 peptide fragment comprising the amino acid sequence of SEQ ID NO. 91 or at least a part of that sequence lacking up to 6 amino acids from the C-terminal.

In a broad aspect the present invention relates to a PD-L1 peptide fragment having the formula:

X¹VILGAILLCLGVALTFIX² wherein

-   N-terminal X¹ is selected from a group consisting of L, HL, THL,     RTHL (SEQ ID NO: 79), -   ERTHL (SEQ ID NO: 80), NERTHL (SEQ ID NO: 81), or is absent, -   C-terminal X² is selected from a group consisting of F, FR, FRL,     FRLR (SEQ ID NO: 82), -   FRLRK (SEQ ID NO: 83), FRLRKG (SEQ ID NO: 84), FRLRKGR (SEQ ID NO:     85), -   FRLRKGRM (SEQ ID NO: 86), FRLRKGRMM (SEQ ID NO: 87), FRLRKGRMMD (SEQ     ID NO: 88), or is absent, -   provided that if X1 is absent, then X2 is not FRLRKG (SEQ ID NO:     84), -   wherein the C-terminal amino acid also comprises the amide,

or a pharmaceutically acceptable salt thereof. The PD-L1 peptide fragment may be selected from any of those disclosed in Table A, or a pharmaceutically acceptable salt thereof, optionally wherein the C terminal amino acid is replaced with the corresponding amide form. As used herein any amino acid sequence shown may be modified at the C-terminal amino acid to be on amide form (—CONH₂) or may be on acid form (—COOH), thus any one of these are preferred embodiments, and it is intended that any C-terminal amino acid, such as I, F, R, L, K, G, M, D comprises both amide and acid form unless specified by —NH₂ or —OH.

In a further embodiment X¹ is selected from the group consisting of RTHL (SEQ ID NO: 79) and NERTHL (SEQ ID NO: 81).

In a still further embodiment X² is selected from the group consisting of FRLRKGROH (SEQ ID NO: 85), FRLRKGR-NH₂ (SEQ ID NO: 85 with C terminal amide) and FRLRKGRMMD-OH (SEQ ID NO: 88).

In one embodiment the peptide fragment of the present invention is selected from

-   NERTHLVILGAILLCLGVALTFIFRLRKGRMMD-OH (SEQ ID NO: 77), -   NERTHLVILGAILLCLGVALTFIFRLRKGRMMD-NH₂ (SEQ ID NO: 77 with C terminal     amide), -   RTHLVILGAILLCLGVALTFIFRLRKGR-OH (SEQ ID NO: 52), -   RTHLVILGAILLCLGVALTFIFRLRKGR-NH₂ (SEQ ID NO: 52 with C terminal     amide), -   NERTHLVILGAILLCLGVALTFI-OH (SEQ ID NO: 67), -   NERTHLVILGAILLCLGVALTFI-NH₂ (SEQ ID NO: 67 with C terminal amide), -   VILGAILLCLGVALTFI-OH (SEQ ID NO: 2), -   VILGAILLCLGVALTFI-NH₂ (SEQ ID NO: 2 with C terminal amide), or -   a pharmaceutically acceptable salt thereof. Typically, the peptide     fragment is selected from -   NERTHLVILGAILLCLGVALTFIFRLRKGRMMD-OH (SEQ ID NO: 77), -   RTHLVILGAILLCLGVALTFIFRLRKGR-OH (SEQ ID NO: 52), and -   RTHLVILGAILLCLGVALTFIFRLRKGR-NH₂ (SEQ ID NO: 52 with C terminal     amide).

In a further aspect the present invention relates to a composition comprising the PD-L1 peptide fragment of the present invention; optionally together with a pharmaceutically acceptable additive. In further embodiments the PD-L1 peptide fragment of the present invention is selected form any one of the above in relation to the broad aspect. Typically, a pharmaceutically acceptable additive is present. In an embodiment the composition is a vaccine composition. In a further embodiment the additive is selected from carriers, excipients, diluents, and adjuvants, typically adjuvants. Such adjuvants may be selected form the group consisting of bacterial DNA based adjuvants, oil/surfactant based adjuvants, viral dsRNA based adjuvants, imidazochinilines, a Montanide ISA adjuvant.

In a still further aspect the present invention relates to an immunotherapeutic composition comprising

-   a) the PD-L1 peptide fragment of the present invention; and -   b) an adjuvant;

for use as a medicament. In further embodiments the PD-L1 peptide fragment of the present invention is selected form any one of the above in relation to the broad aspect. In further embodiments the adjuvants may be selected form the group consisting of bacterial DNA based adjuvants, oil/surfactant based adjuvants, viral dsRNA based adjuvants, imidazochinilines, a Montanide ISA adjuvant. Each of these adjuvants or group of adjuvants constitute an individual embodiment.

In an embodiment the immunotherapeutic composition of the present invention is for use in a method for treatment or prevention of a disease, disorder or condition selected from cancer, such as a tumor forming cancer disease; an infection, such as an infectious disease, e.g. an intracellular infection, for example an intracellular infection with a pathogen selected from the group consisting of L. monocytogenes and plasmodium, a viral infection, for example an infection with a virus selected from the group consisting of HIV and hepatitis; an autoimmune disease, such as diabetes, SLE and sclerosis. Each of the disease, disorder or condition or group of disease, disorder or condition constitute an individual embodiment.

In a further aspect the present invention relates to a kit-of-parts comprising:

a) the immunotherapeutic composition of the present invention, and

b) a composition comprising at least one second active ingredient, selected from an immunostimulating compound, such as an interleukin, e.g. IL-2 and or IL-21, an anti-cancer agent, such as a chemotherapeutic agent, e.g. Actimide, Azacitidine, Azathioprine, Bleomycin, Carboplatin, Capecitabine, Cisplatin, Chlorambucil, Cyclophosphamide, Cytarabine, Daunorubicin, Docetaxel, Doxifluridine, Doxorubicin, Epirubicin, Etoposide, Fludarabine, Fluorouracil, Gemcitabine, Hydroxyurea, Idarubicin, Irinotecan, Lenalidomide, Leucovorin, Mechlorethamine, Melphalan, Mercaptopurine, Methotrexate, Mitoxantrone, nivolumab, Oxaliplatin, Paclitaxel, pembrolizumab, Pemetrexed, Revlimid, Temozolomide, Teniposide, Thioguanine, Valrubicin, Vinblastine, Vincristine, Vindesine and Vinorelbine. In an embodiment the provided compositions are to be administered simultaneously. In another embodiment the provided compositions are to be administered sequentially. In respect of the immunotherapeutic composition under a) further embodiments of the PD-L1 peptide fragment of the present invention is selected form any one of the above in relation to the broad aspect. In further embodiments the adjuvants may be selected form the group consisting of bacterial DNA based adjuvants, oil/surfactant based adjuvants, viral dsRNA based adjuvants, imidazochinilines, a Montanide ISA adjuvant. Each of these adjuvants or group of adjuvants constitute an individual embodiment. In respect of the second active ingredient under b) further embodiments of the second active ingredient is selected form any one of the above which constitutes individual embodiments.

In a further aspect the present invention relates to a kit-of-parts comprising:

a) the immunotherapeutic composition of the present invention, and

b) an immunomodulatory agent which blocks or inhibits an immune system checkpoint, which checkpoint may be the same as, or different from, the checkpoint of which the composition of (a) comprises a component. In other words, it may be the same as, or different from, the checkpoint which comprises the interaction between PD1 and PDL1.

-   -   In an embodiment the checkpoint is selected from the following:         -   a) The interaction between IDO1 and its substrate;         -   b) The interaction between PD1 and PDL1 and/or PD1 and PDL2;         -   c) The interaction between CTLA4 and CD86 and/or CTLA4 and             CD80;         -   d) The interaction between B7-H3 and/or B7-H4 and their             respective ligands;         -   e) The interaction between HVEM and BTLA;         -   f) The interaction between GAL9 and TIM3;         -   g) The interaction between MHC class I or II and LAG3; and         -   h) The interaction between MHC class I or II and KIR

In a further embodiment the immunomodulatory agent is an antibody or small molecule inhibitor (SMI) which binds to a component of a said immune system checkpoint.

In a further embodiment the agent is a small molecule inhibitor of IDO1, optionally wherein said inhibitor is Epacadostat (INCB24360), Indoximod, GDC-0919 (NLG919) or F001287, or wherein said agent is an antibody which binds to CTLA4 or PD1, optionally wherein said antibody which binds to CTLA4 is ipilimumab and said antibody which binds to PD1 is pembrolizumab.

In a still further aspect the present invention relates to a method of treating a clinical condition characterized by expression of PD-L1, the method comprising administering to an individual suffering from said clinical condition an effective amount of the peptide fragment of the present invention, the composition of the present invention, or the kit-of-parts of the present invention.

In a still further aspect the present invention relates to a method of treating a clinical condition characterized by expression of PD-L1, the method comprising administering to an individual suffering from said clinical condition an effective amount of a PD-L1 peptide fragment having the formula:

X¹VILGAILLCLGVALTFIX² wherein

-   N-terminal X¹ is selected from a group consisting of L, HL, THL,     RTHL (SEQ ID NO: 79), -   ERTHL (SEQ ID NO: 80), NERTHL (SEQ ID NO: 81), or is absent, -   C-terminal X² is selected from a group consisting of F, FR, FRL,     FRLR (SEQ ID NO: 82), -   FRLRK (SEQ ID NO: 83), FRLRKG (SEQ ID NO: 84), FRLRKGR (SEQ ID NO:     85), -   FRLRKGRM (SEQ ID NO: 86), FRLRKGRMM (SEQ ID NO: 87), FRLRKGRMMD (SEQ     ID NO: 88), or is absent, -   provided that if X1 is absent, then X2 is not FRLRKG (SEQ ID NO:     84), -   wherein the C-terminal amino acid also comprises the amide, or -   a pharmaceutically acceptable salt thereof. The PD-L1 peptide     fragment may be selected from any of those disclosed in Table A, or     a pharmaceutically acceptable salt thereof, optionally wherein the C     terminal amino acid is replaced with the corresponding amide form.

In a further aspect the present invention relates to use of a PD-L1 peptide fragment of the present invention for the manufacture of a medicament, such as an immunotherapeutic composition or vaccine, for the treatment or prevention of a clinical condition characterized by expression of PD-L1. In an embodiment of the use of a peptide fragment of the present invention the medicament is an immunotherapeutic composition. In another embodiment of the use of a peptide fragment of the present invention the medicament is vaccine. In one embodiment the clinical condition to be treated is a cancer disease where PD-L1 is expressed. In another embodiment the clinical condition is selected from the group consisting of infectious diseases and autoimmune diseases. In a further embodiment the PD-L1 peptide fragment has the formula:

X¹VILGAILLCLGVALTFIX² wherein

-   N-terminal X¹ is selected from a group consisting of L, HL, THL,     RTHL (SEQ ID NO: 79), -   ERTHL (SEQ ID NO: 80), NERTHL (SEQ ID NO: 81), or is absent, -   C-terminal X² is selected from a group consisting of F, FR, FRL,     FRLR (SEQ ID NO: 82), -   FRLRK (SEQ ID NO: 83), FRLRKG (SEQ ID NO: 84), FRLRKGR (SEQ ID NO:     85), -   FRLRKGRM (SEQ ID NO: 86), FRLRKGRMM (SEQ ID NO: 87), FRLRKGRMMD (SEQ     ID NO: 88), or is absent, -   provided that if X1 is absent, then X2 is not FRLRKG (SEQ ID NO:     84), -   wherein the C-terminal amino acid also comprises the amide, or -   a pharmaceutically acceptable salt thereof. The PD-L1 peptide     fragment may be selected from any of those disclosed in Table A, or     a pharmaceutically acceptable salt thereof, optionally -   wherein the C terminal amino acid is replaced with the corresponding     amide form.

In a still further aspect the present invention relates to a PD-L1 peptide fragment having the formula:

X¹VILGAILLCLGVALTFIX² wherein

-   N-terminal X¹ is selected from a group consisting of L, HL, THL,     RTHL (SEQ ID NO: 79), -   ERTHL (SEQ ID NO: 80), NERTHL (SEQ ID NO: 81), or is absent, -   C-terminal X² is selected from a group consisting of F, FR, FRL,     FRLR (SEQ ID NO: 82), -   FRLRK (SEQ ID NO: 83), FRLRKG (SEQ ID NO: 84), FRLRKGR (SEQ ID NO:     85), -   FRLRKGRM (SEQ ID NO: 86), FRLRKGRMM (SEQ ID NO: 87), FRLRKGRMMD (SEQ     ID NO: 88), or is absent, -   provided that if X1 is absent, then X2 is not FRLRKG (SEQ ID NO:     84), -   wherein the C-terminal amino acid also comprises the amide, or -   a pharmaceutically acceptable salt thereof; -   for use in a method for treatment or prevention of a cancer, when     administered simultaneously or sequentially with an additional     cancer therapy. The PD-L1 peptide fragment may be selected from any     of those disclosed in Table A, or a pharmaceutically acceptable salt     thereof, optionally wherein the C terminal amino acid is replaced     with the corresponding amide form. The additional cancer therapy may     be a cytokine therapy, a T-cell therapy, an NK therapy, an immune     system checkpoint inhibitor, chemotherapy, radiotherapy,     immunostimulating substances, gene therapy, antibodies and dendritic     cells. Each of the additional cancer therapies that is a cytokine     therapy, a T-cell therapy, an NK therapy, an immune system     checkpoint inhibitor, chemotherapy, radiotherapy, immunostimulating     substances, gene therapy, antibodies and dendritic cells constitutes     individual embodiments. For instance, in a further embodiment the     additional cancer therapy is selected from an immune system     checkpoint inhibitor, wherein the inhibitor is a checkpoint blocking     antibody selected from Actimide, Azacitidine, Azathioprine,     Bleomycin, Carboplatin, Capecitabine, Cisplatin, Chlorambucil,     Cyclophosphamide, Cytarabine, Daunorubicin, Docetaxel,     Doxifluridine, Doxorubicin, Epirubicin, Etoposide, Fludarabine,     Fluorouracil, Gemcitabine, Hydroxyurea, Idarubicin, Irinotecan,     Lenalidomide, Leucovorin, Mechlorethamine, Melphalan,     Mercaptopurine, Methotrexate, Mitoxantrone, Nivolumab, Oxaliplatin,     Paclitaxel, Pembrolizumab, Pemetrexed, Revlimid, Temozolomide,     Teniposide, Thioguanine, Valrubicin, Vinblastine, Vincristine,     Vindesine and Vinorelbine. In an embodiment the PD-L1 peptide     fragment is selected from -   NERTHLVILGAILLCLGVALTFIFRLRKGRMMD (SEQ ID NO: 77), -   NERTHLVILGAILLCLGVALTFIFRLRKGRMMD-NH2 (SEQ ID NO: 77 with C terminal     amide), -   RTHLVILGAILLCLGVALTFIFRLRKGR (SEQ ID NO: 52), -   RTHLVILGAILLCLGVALTFIFRLRKGR-NH2 (SEQ ID NO: 52 with C terminal     amide), -   NERTHLVILGAILLCLGVALTFI (SEQ ID NO: 67) -   NERTHLVILGAILLCLGVALTFI-NH₂ (SEQ ID NO: 67 with C terminal amide), -   VILGAILLCLGVALTFI (SEQ ID NO: 2), -   VILGAILLCLGVALTFI-NH₂ (SEQ ID NO: 2 with C terminal amide), or -   a pharmaceutically acceptable salt thereof. Typically, the peptide     fragment is selected from -   NERTHLVILGAILLCLGVALTFIFRLRKGRMMD (SEQ ID NO: 77), -   RTHLVILGAILLCLGVALTFIFRLRKGR (SEQ ID NO: 52), and -   RTHLVILGAILLCLGVALTFIFRLRKGR-NH₂ (SEQ ID NO: 52 with C terminal     amide).

In a further aspect the present invention relates to a PD-L1 peptide fragment comprising the formula:

FMTYWHLLNAFTVTVPKDL (SEQ ID NO: 89) wherein the C-terminal amino acid also comprises the amide, or a pharmaceutically acceptable salt thereof;

for use in a method for treatment or prevention of a cancer, when administered simultaneously or sequentially with an additional cancer therapy, such as a cytokine therapy, a T-cell therapy, an NK therapy, an immune system checkpoint inhibitor, chemotherapy, radiotherapy, immunostimulating substances, gene therapy, antibodies and dendritic cells. In an embodiment the PD-L1 peptide fragment consists of up to 35 consecutive amino acids, such 30, or 25, of the sequence of SEQ ID NO. 1 and comprises the PD-L1 fragment having the formula: FMTYWHLLNAFTVTVPKDL (SEQ ID NO: 89). In an embodiment the PD-L1 peptide fragment is selected from the PD-L1 fragment having the formula: FMTYWHLLNAFTVTVPKDL (SEQ ID NO: 89) wherein the C-terminal amino acid also comprises the amide. In a further embodiment the additional cancer therapy is selected from an immune system checkpoint inhibitor, wherein the inhibitor is a checkpoint blocking antibody selected from Actimide, Azacitidine, Azathioprine, Bleomycin, Carboplatin, Capecitabine, Cisplatin, Chlorambucil, Cyclophosphamide, Cytarabine, Daunorubicin, Docetaxel, Doxifluridine, Doxorubicin, Epirubicin, Etoposide, Fludarabine, Fluorouracil, Gemcitabine, Hydroxyurea, Idarubicin, Irinotecan, Lenalidomide, Leucovorin, Mechlorethamine, Melphalan, Mercaptopurine, Methotrexate, Mitoxantrone, Nivolumab, Oxaliplatin, Paclitaxel, Pembrolizumab, Pemetrexed, Revlimid, Temozolomide, Teniposide, Thioguanine, Valrubicin, Vinblastine, Vincristine, Vindesine and Vinorelbine.

The PD-L1 peptide fragments disclosed herein are made by standard peptide synthesis, such as solid-phase peptide synthesis (SPPS). SPPS is a standard method for synthesizing peptides in the lab. SPPS allows for the synthesis of natural peptides which are difficult to express in bacteria, the incorporation of unnatural amino acids, peptide/protein backbone modification, and the synthesis of D-proteins, which consist of D-amino acids. Small porous beads are treated with functional units ('linkers') on which peptide chains can be built. The peptide will remain covalently attached to the bead until cleaved from it by a reagent such as anhydrous hydrogen fluoride or trifluoroacetic acid. The peptide is thus ‘immobilized’ on the solid-phase and can be retained during a filtration process while liquid-phase reagents and by-products of synthesis are flushed away. The general principle of SPPS is one of repeated cycles of deprotection-wash-coupling-wash. The free N-terminal amine of a solid-phase attached peptide is coupled to a single N-protected amino acid unit. This unit is then deprotected, revealing a new N-terminal amine to which a further amino acid may be attached. The superiority of this technique partially lies in the ability to perform wash cycles after each reaction, removing excess reagent with all of the growing peptide of interest remaining covalently attached to the insoluble resin. There are two majorly used forms of SPPS—Fmoc and Boc. Unlike ribosome protein synthesis, solid-phase peptide synthesis proceeds in a C-terminal to N-terminal fashion. The N-termini of amino acid monomers is protected by either of these two groups and added onto a deprotected amino acid chain. Automated synthesizers are available for both techniques, though many research groups continue to perform SPPS manually. Furthermore, the skilled person will understand that the processes described above and hereinafter the functional groups of intermediate compounds may need to be protected by protecting group.

When the compounds and pharmaceutical compositions herein disclosed are used for the above treatment, a therapeutically effective amount of at least one compound is administered to a mammal in need of said treatment.

As used herein amino acids are identified by the one or three letter code known to the person skilled in the art and shown in the table below for convenience:

Amino Acids, One and Three Letter Codes

Amino acid Three letter code One letter code Alanine ala A Arginine arg R Asparagine asn N aspartic acid asp D asparagine or aspartic acid asx B Cysteine cys C glutamic acid glu E Glutamine gln Q glutamine or glutamic acid glx Z Glycine gly G Histidine his H Isoleucine ile I Leucine leu L Lysine lys K Methionine met M Phenylalanine phe F Proline pro P Serine ser S Threonine thr T Tryptophan trp W Tyrosine tyr Y Valine val V

The term “treatment” and “treating” as used herein means the management and care of a patient for the purpose of combating a condition, such as a disease or a disorder. The term is intended to include the full spectrum of treatments for a given condition from which the patient is suffering, such as administration of the active compound to alleviate the symptoms or complications, to delay the progression of the disease, disorder or condition, to alleviate or relief the symptoms and complications, and/or to cure or eliminate the disease, disorder or condition as well as to prevent the condition, wherein prevention is to be understood as the management and care of a patient for the purpose of combating the disease, condition, or disorder and includes the administration of the active compounds to prevent the onset of the symptoms or complications. The treatment may either be performed in an acute or in a chronic way. The patient to be treated is preferably a mammal; in particular a human being, but it may also include animals, such as dogs, cats, cows, sheep and pigs.

The term “a therapeutically effective amount” of a PD-L1 peptide fragment of the present invention or a peptide fragment as disclosed herein, as used herein means an amount sufficient to cure, alleviate or partially arrest the clinical manifestations of a given disease and its complications. An amount adequate to accomplish this is defined as “therapeutically effective amount”. Effective amounts for each purpose will depend on the severity of the disease or injury as well as the weight and general state of the subject. It will be understood that determining an appropriate dosage may be achieved using routine experimentation, by constructing a matrix of values and testing different points in the matrix, which is all within the ordinary skills of a trained physician or veterinary.

In a still further aspect the present invention relates to a pharmaceutical composition comprising the PD-L1 peptide fragment of the present invention and optionally a pharmaceutically acceptable additive, such as a carrier or an excipient.

As used herein “pharmaceutically acceptable additive” is intended without limitation to include carriers, excipients, diluents, adjuvant, colorings, aroma, preservatives etc. that the skilled person would consider using when formulating a compound of the present invention in order to make a pharmaceutical composition.

The adjuvants, diluents, excipients and/or carriers that may be used in the composition of the invention must be pharmaceutically acceptable in the sense of being compatible with the compound of formula (1) and the other ingredients of the pharmaceutical composition, and not deleterious to the recipient thereof. It is preferred that the compositions shall not contain any material that may cause an adverse reaction, such as an allergic reaction. The adjuvants, diluents, excipients and carriers that may be used in the pharmaceutical composition of the invention are well known to a person within the art.

Adjuvants are any substance whose admixture into the composition increases or otherwise modifies the immune response elicited by the composition. Adjuvants, broadly defined, are substances which promote immune responses. Adjuvants may also preferably have a depot effect, in that they also result in a slow and sustained release of an active agent from the administration site. A general discussion of adjuvants is provided in Goding, Monoclonal Antibodies: Principles & Practice (2nd edition, 1986) at pages 61-63.

Adjuvants may be selected from the group consisting of: AlK(SO4)2, AlNa(SO4)2, AlNH4 (SO4), silica, alum, Al(OH)3, Ca3 (PO4)2, kaolin, carbon, aluminum hydroxide, muramyl dipeptides, N-acetyl-muramyl-L-threonyl-D-isoglutamine (thr-DMP), N-acetyl-nornuramyl-L-alanyl-D-isoglutamine (CGP 11687, also referred to as nor-MDP), N-acetylmuramyul-L-alanyl-D-isoglutaminyl-L-alanine-2-(1′2′-dipalmitoyl-sn -glycero-3-hydroxphosphoryloxy)-ethylamine (CGP 19835A, also referred to as MTP-PE), RIBI (MPL+TDM+CWS) in a 2% squalene/Tween-80.RTM. emulsion, lipopolysaccharides and its various derivatives, including lipid A, Freund's Complete Adjuvant (FCA), Freund's Incomplete Adjuvants, Merck Adjuvant 65, polynucleotides (for example, poly IC and poly AU acids), wax D from Mycobacterium, tuberculosis, substances found in Corynebacterium parvum, Bordetella pertussis, and members of the genus Brucella, Titermax, ISCOMS, Quil A, ALUN (see US 58767 and U.S. Pat. Nos. 5,554,372), Lipid A derivatives, choleratoxin derivatives, HSP derivatives, LPS derivatives, synthetic peptide matrixes or GMDP, Interleukin 1, Interleukin 2, Montanide ISA-51 and QS-21. Various saponin extracts have also been suggested to be useful as adjuvants in immunogenic compositions. Granulocyte-macrophage colony stimulating factor (GM-CSF) may also be used as an adjuvant.

Preferred adjuvants to be used with the invention include oil/surfactant based adjuvants such as Montanide adjuvants (available from Seppic, Belgium), preferably Montanide ISA-51. Other preferred adjuvants are bacterial DNA based adjuvants, such as adjuvants including CpG oligonucleotide sequences. Yet other preferred adjuvants are viral dsRNA based adjuvants, such as poly I:C. GM-CSF and Imidazochinilines are also examples of preferred adjuvants.

The adjuvant is most preferably a Montanide ISA adjuvant. The Montanide ISA adjuvant is preferably Montanide ISA 51 or Montanide ISA 720.

In Goding, Monoclonal Antibodies: Principles & Practice (2nd edition, 1986) at pages 61-63 it is also noted that, when an antigen of interest is of low molecular weight, or is poorly immunogenic, coupling to an immunogenic carrier is recommended. A polypeptide or fragment of an immunotherapeutic composition of the invention may be coupled to a carrier. A carrier may be present independently of an adjuvant. The function of a carrier can be, for example, to increase the molecular weight of a polypeptide fragment in order to increase activity or immunogenicity, to confer stability, to increase the biological activity, or to increase serum half-life. Furthermore, a carrier may aid in presenting the polypeptide or fragment thereof to T-cells. Thus, in the immunogenic composition, the polypeptide or fragment thereof may be associated with a carrier such as those set out below.

The carrier may be any suitable carrier known to a person skilled in the art, for example a protein or an antigen presenting cell, such as a dendritic cell (DC). Carrier proteins include keyhole limpet hemocyanin, serum proteins such as transferrin, bovine serum albumin, human serum albumin, thyroglobulin or ovalbumin, immunoglobulins, or hormones, such as insulin or palmitic acid. Alternatively, the carrier protein may be tetanus toxoid or diphtheria toxoid. Alternatively, the carrier may be a dextran such as sepharose. The carrier must be physiologically acceptable to humans and safe.

The immunotherapeutic composition may optionally comprise a pharmaceutically acceptable excipient. The excipient must be ‘acceptable’ in the sense of being compatible with the other ingredients of the composition and not deleterious to the recipient thereof. Auxiliary substances, such as wetting or emulsifying agents, pH buffering substances and the like, may be present in the excipient. These excipients and auxiliary substances are generally pharmaceutical agents that do not induce an immune response in the individual receiving the composition, and which may be administered without undue toxicity. Pharmaceutically acceptable excipients include, but are not limited to, liquids such as water, saline, polyethyleneglycol, hyaluronic acid, glycerol and ethanol. Pharmaceutically acceptable salts can also be included therein, for example, mineral acid salts such as hydrochlorides, hydrobromides, phosphates, sulfates, and the like; and the salts of organic acids such as acetates, propionates, malonates, benzoates, and the like. A thorough discussion of pharmaceutically acceptable excipients, vehicles and auxiliary substances is available in Remington's Pharmaceutical Sciences (Mack Pub. Co., N.J. 1991).

The immunotherapeutic composition may be prepared, packaged, or sold in a form suitable for bolus administration or for continuous administration. Injectable compositions may be prepared, packaged, or sold in unit dosage form, such as in ampoules or in multi-dose containers containing a preservative. Compositions include, but are not limited to, suspensions, solutions, emulsions in oily or aqueous vehicles, pastes, and implantable sustained-release or biodegradable formulations. In one embodiment of a composition, the active ingredient is provided in dry (for e.g., a powder or granules) form for reconstitution with a suitable vehicle (e. g., sterile pyrogen-free water) prior to administration of the reconstituted composition. The composition may be prepared, packaged, or sold in the form of a sterile injectable aqueous or oily suspension or solution. This suspension or solution may be formulated according to the known art, and may comprise, in addition to the active ingredient, additional ingredients such as the adjuvants, excipients and auxiliary substances described herein. Such sterile injectable formulations may be prepared using a non-toxic parenterally-acceptable diluent or solvent, such as water or 1,3-butane diol, for example. Other acceptable diluents and solvents include, but are not limited to, Ringer's solution, isotonic sodium chloride solution, and fixed oils such as synthetic mono- or di-glycerides.

Other compositions which are useful include those which comprise the active ingredient in microcrystalline form, in a liposomal preparation, or as a component of a biodegradable polymer systems. Compositions for sustained release or implantation may comprise pharmaceutically acceptable polymeric or hydrophobic materials such as an emulsion, an ion exchange resin, a sparingly soluble polymer, or a sparingly soluble salt. Alternatively, the active ingredients of the composition may be encapsulated, adsorbed to, or associated with, particulate carriers. Suitable particulate carriers include those derived from polymethyl methacrylate polymers, as well as PLG microparticles derived from poly(lactides) and poly(lactide-co-glycolides). See, e.g., Jeffery et al. (1993) Pharm. Res. 10:362-368. Other particulate systems and polymers can also be used, for example, polymers such as polylysine, polyarginine, polyornithine, spermine, spermidine, as well as conjugates of these molecules.

As mentioned above, the compositions and particularly immunotherapetic compositions as herein disclosed may, in addition to the compounds herein disclosed, further comprise at least one pharmaceutically acceptable adjuvant, diluent, excipient and/or carrier. In some embodiments, the pharmaceutical compositions comprise from 1 to 99 weight % of said at least one pharmaceutically acceptable adjuvant, diluent, excipient and/or carrier and from 1 to 99 weight % of a compound as herein disclosed. The combined amount of the active ingredient and of the pharmaceutically acceptable adjuvant, diluent, excipient and/or carrier may not constitute more than 100% by weight of the composition, particularly the pharmaceutical composition. Any composition, vaccine, or kit as described herein may additionally comprise a preservative, which may improve the stability of the component peptide fragments of the invention when stored in solution or as a lyophilisate. Suitable preservatives are well known in the art and are preferably pharmaceutically acceptable. In some cases stability of the peptide fragments may be increased by the incorporation of additional terminal residues, at the N terminus, at the C terminus, or at both termini. Such residues would typically be hydrophilic amino acid residues or corresponding amides. Typically the peptide fragments may include an additional 1, 2 or 3 such residues at the N and/or C termini

In some embodiments, only one compound as herein disclosed is used for the purposes discussed above.

In some embodiments, two or more of the compound as herein disclosed are used in combination for the purposes discussed above.

The composition, particularly immunotherapetic composition comprising a compound set forth herein may be adapted for oral, intravenous, topical, intraperitoneal, nasal, buccal, sublingual, or subcutaneous administration, or for administration via the respiratory tract in the form of, for example, an aerosol or an air-suspended fine powder. Therefore, the pharmaceutical composition may be in the form of, for example, tablets, capsules, powders, nanoparticles, crystals, amorphous substances, solutions, transdermal patches or suppositories.

Further embodiments of the process are described in the experimental section herein, and each individual process as well as each starting material constitutes embodiments that may form part of embodiments.

The above embodiments should be seen as referring to any one of the aspects (such as ‘method for treatment’, ‘immunotherapetic composition’, ‘compound for use as a medicament’, or ‘compound for use in a method’) described herein as well as any one of the embodiments described herein unless it is specified that an embodiment relates to a certain aspect or aspects of the present invention.

All references, including publications, patent applications and patents, cited herein are hereby incorporated by reference to the same extent as if each reference was individually and specifically indicated to be incorporated by reference and was set forth in its entirety herein.

All headings and sub-headings are used herein for convenience only and should not be construed as limiting the invention in any way.

Any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.

The terms “a” and “an” and “the” and similar referents as used in the context of describing the invention are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context.

Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless other-wise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. Unless otherwise stated, all exact values provided herein are representative of corresponding approximate values (e.g., all exact exemplary values provided with respect to a particular factor or measurement can be considered to also pro-vide a corresponding approximate measurement, modified by “about,” where appropriate).

All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context.

The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise indicated. No language in the specification should be construed as indicating any element is essential to the practice of the invention unless as much is explicitly stated.

The citation and incorporation of patent documents herein is done for convenience only and does not reflect any view of the validity, patentability and/or enforceability of such patent documents.

The description herein of any aspect or embodiment of the invention using terms such as “comprising”, “having”, “including” or “containing” with reference to an element or elements is intended to provide support for a similar aspect or embodiment of the invention that “consists of”, “consists essentially of”, or “substantially comprises” that particular element or elements, unless otherwise stated or clearly contradicted by context (e.g., a composition described herein as comprising a particular element should be understood as also describing a composition consisting of that element, unless otherwise stated or clearly contradicted by context).

This invention includes all modifications and equivalents of the subject matter recited in the aspects or claims presented herein to the maximum extent permitted by applicable law.

The present invention is further illustrated by the following examples that, however, are not to be construed as limiting the scope of protection. The features disclosed in the foregoing description and in the following examples may, both separately and in any combination thereof, be material for realizing the invention in diverse forms thereof.

EXAMPLES Example 1 Materials and Methods

Patients and Donors 26 stage IV melanoma patients were enrolled in an open-labeled, non-randomized phase I/II study (EudraCT number 2009-010194-20; Clinicaltrials.gov identifier: NCT00978913). The protocol was approved by the Scientific Ethics Committee for The Capital Region of Denmark (H-A-2009-013), the Danish Medicines Agency (2612-4030), the Danish Data Protection Agency and conducted in accordance with the provisions of the Declaration of Helsinki. Written informed consent from the patients was obtained before study entry. The clinical and immunological results will be reported elsewhere (Borch et al., in preparation). In short patients were injected with autologous DC vaccines intradermally fortnightly six times and subsequently every four weeks until progression. Concomitantly, patients were treated with a metronomic cyclophosphamide regimen (50 mg twice a day) biweekly.

For immune monitoring purposes Peripheral Blood Mononuclear Cells (PBMC) were collected from patients before vaccination, after four and six vaccinations with a dendritic cell vaccine (DCvacc). PBMC were isolated using Lymphoprep separation, HLA-typed and frozen in FCS with 10% DMSO. DC vaccines were generated as previously described²⁴ and all procedures were performed according to Good Manufacturing Practice (GMP) as approved by the Danish Medicines Agency. In short, autologous PBMCs were isolated by leukapheresis, and monocytes were further isolated and cultured for 8 days. On day 6, maturation of DCs was performed using IL-1β, TNFα, IL-6, and PGE2. Aliquots of 1×10⁷ DCs were frozen using automated cryopreservation. The matured DCs were transfected with mRNA encoding the tumor associated antigens p53, survivin and hTERT to generate DCvacc.

Peptides

A 19 amino acid long polypeptide from PD-L1 was synthesized (TAG Copenhagen, Copenhagen, Denmark): PDLong1: PDL19-28, FMTYWHLLNAFTVTVPKDL—SEQ ID NO: 89. PDLong1 included sequence of 9mer HLA-A2 restricted peptide (here entitled “PD-L101”) PDL1₁₅₋₂₃; (LLNAFTVTV—SEQ ID NO: 90) identified and analyzed using the epitope prediction Database “SYFPEITHI” available on the internet²⁵. PD-L101 scored 30 by the SYFPEITHI algorithm and came out as the top candidate epitope.

In addition a 23 amino acid long from PD-L1 was synthesized (TAG Copenhagen, Copenhagen, Denmark): PDLong2:PDL1₂₄₂₋₂₆₄, VILGAILLCLGVALTFIFRLRKG (SEQ ID NO: 91). This long peptide contains a number of possible 15'mer HLA class II-restricted as well as minimal class I-restricted epitopes as predicted by the algorithm developed by Rammensee et al. available at www.syfpeithi.de²⁵. Especially it contains the HLA-A2 epitope entitled PDL111 PDL1₂₅₀₋₅₈, CLGVALTFI—SEQ ID NO: 92). A 20-mer long peptide (here entitled ‘irrelevant control’) GARVERVDFGNFVFNISVLW—SEQ ID NO: 93- was used as control peptide as well as the HLA-A2 high affinity binding epitope HIV-1 pol₄₇₆-484 (ILKEPVHGV—SEQ ID NO: 94) was used as irrelevant controls.

Co-Stimulation Assays

PBMCs from malignant melanoma patients were stimulated with autologous DCvacc with ratio 1:10 DCvacc:PBMCs. A day after stimulation, cultures were divided and co-stimulated with peptides either with 25 μg/mL of PDLong1: PDL19-28, [FMTYWHLLNAFTVTVPKDL SEQ ID NO: 89] or PDLong2: PDL1242-264, [VILGAILLCLGVALTFIFRLRKG—SEQ ID NO: 91] or irrelevant long peptide [GARVERVDFGNFVFNISVLW—SEQ ID NO: 93] as control co-stimulation. Second stimulation with DCvacc was performed on day 7 and followed by peptide co-stimulation on day 8. IL-2 (120 U/mL) was added a day after each peptide costimulations. A week after second peptide co-stimulation the cultures were analyzed for DCvacc response using intracellular cytokine staining.

Intracellular Cytokine Staining (ICS)

For detection of cell subpopulations producing cytokines (IFN-γ and TNF-α), PBMCs that were stimulated with DCvacc and co-stimulated with peptides for two weeks, were stimulated with DCvacc (ratio 1:10 DCvacc:PBMCs) for 5 hours at 37° C. with 5% CO₂. GolgiPlug (BD) was added at a dilution of 1:200 after the first hour of incubation. After 4 additional hours cells were washed twice with PBS, stained fluorochrome conjugated antibodies for surface markers (CD3-Amcyan, CD4-PerCP and CD8-Pacific Blue, all from BD). Cells were washed one additional time and thereafter were fixed and permeabilized with Fixation/Permeabilization and Permeabilization Buffer (eBioscience), according to manufacturer's instructions. Cells were subsequently stained with fluorochrome-conjugated antibodies for intracellular cytokines. The following combinations were used: IFN-γ-PE-CY7 (BD), TNF-α-APC (eBioscience). Relevant isotype controls were used to enable correct compensation and confirm antibody specificity. Stained cells were analyzed using a BD FACSCanto II flow cytometer and further analysis was performed with BD FacsDiva Software.

To determine PD-L1 response, cultures were stimulated with PDLong1 or PDLong2 (0.2 mmol/L) or an irrelevant peptide for 5 hr. Subsequently cells were stained surface and intra-cellular antibodies and further analysed on BD FACSCanto II.

ELISPOT

In the present study the ELISPOT was performed according to the guidelines provided by CIP (http://cimt.eu/cimt/files/d1/cip_guidelines.pdf). Briefly, nitrocellulose bottomed 96-well plates (MultiScreen MAIP N45; Millipore) were coated overnight with the relevant antibodies. The wells were washed, blocked by X-vivo medium and the cells were added if possible in triplicates otherwise in duplicates at different cell concentrations, with or without peptide. The plates were incubated four hours. Next, medium was discarded and the wells were washed prior to addition of the relevant biotinylated secondary Ab (Mabtech), followed by the Avidinenzyme conjugate (AP-Avidin; Calbiochem/Invitrogen Life Technologies) and finally the enzyme substrate NBT/BCIP (Invitrogen Life Technologies). The spots were counted using the ImmunoSpot Series 2.0 Analyzer (CTL Analyzers).

CBA

To determine the changes in cytokine secretion in DCvacc stimulated and peptide co-stimulated (PDLong1 and PDLong2 or HIV peptide) cultures, cell culture supernatants were analyzed using BD™ Cytometric Bead Array (CBA) Flex Sets for IFN-γ, TGF-β1, TNF-α, IL-6, IL-10 and IL-17A. Flex sets for IFN-γ, TNF-α, IL-6 and IL-10 were combined, whereas IL-17A and TGF-β1 were analyzed separately. Analysis was performed according to the manufacturer's recommendations. Samples were acquired on FACSCANTO II (BD Biosciences) and data was analyzed using FCAP Array™ Software v 3.0.1 (BD Biosciences).

Results

Co-Stimulation with a Long PD-L1 Peptide Boosts T Cell Reactivity Against DCvacc

In general, low immunity toward DCvacc was observed in the patients both before and after vaccination. In the present study, we set out to examine the supporting effects of PD-L1—specific T cells on the DCvacc-specific T cell response. Hence, PBMCs were isolated from patients with melanoma at baseline before vaccination as well as after four and, for some patients, after six vaccinations with DCvacc. PBMCs were stimulated twice with DCvacc in combination with either a control HIV epitope or PD-L1 peptides, as shown in FIG. 1A. Overall, we found that DCvacc mainly stimulates CD4⁺ T cells. First we examined the effects of a previously described long T cell epitope from PD-L1 (“PDLong1” [PDL1_(9-27,) FMTYWHLLNAFTVTVPKDL] SEQ ID NO: 89).¹⁸ PDLong1 includes an HLA-A2-restricted, PD-L1-derived CD8⁺ T cell epitope (PDL1₁₅₋₂₃, LLNAFTVTV—SEQ ID NO: 90). We observed an increase in the number of PBMCs that showed reactivity against DCvacc when they were cocultured with PDLong1 compared to the control HIV epitope. FIG. 1B-E shows the results of cultures from three donors in which coactivation of PD-L1-specific T cells significantly boosted T cell immunity toward DCvacc. CD4⁺ T cells released TNFα alone in response to DCvacc without co-stimulation (FIG. 1B). TNFα/INFγ double-positive CD4⁺ T cells were induced by DCvacc with PD-L1 peptide co-stimulation (FIG. 1C). Reactive CD4⁺ and CD8⁺ T cell numbers both increased in response to DCvacc with PD-L1 peptide co-stimulation (FIGS. 1D and E).

In cultures of PBMCs before vaccination, co-stimulation with PDLong1 increased CD4⁺ T cell reactivity toward DCvacc in six out of eight donors (P=0.312) and CD8⁺ T cell reactivity in seven out of eight donors (P=0.039) (FIG. 2A and B, respectively). After four vaccinations, CD4⁺ T cell reactivity was increased in all donors (P=0.016) (FIG. 2A), whereas CD8⁺ T cell reactivity was increased in only five out of eight donors (P=0.313) (FIG. 2B). Both CD4⁺ and CD8⁺ T cells reacted to a significantly greater extent against DCvacc in cultures co-stimulated with PDLong1 peptide compared to cultures co-stimulated with control peptide (P=0.02 and P=0.05, respectively).

Spontaneous Immune Response Against a Novel Long PD-L1 Epitope

To further investigate whether the immune response against PD-L1 could be augmented by co-stimulation, we used the IFNγ ELISPOT assay to examine tumor-infiltrating lymphocytes from 12 melanoma patients for T cell reactivity against an additional PD-L1 derived epitope (PDLong2 [PDL1₂₄₂₋₂₆₄, VILGAILLCLGVALTFIFRLRKG (SEQ ID NO: 91)]). The IFNγ ELISPOT assay revealed an increased T cell response in tumor-infiltrating lymphocytes cultured with PDLong2 (FIG. 3A and B). This increased response was confirmed by intracellular cytokine staining (FIG. 3C and D).

Co-Stimulation with Two Long PD-L1 Peptides Boosts T Cell Reactivity Against DCvacc

Next, we examined PBMCs from eight vaccinated melanoma patients to determine the effects of co-stimulation with both PDLong1 and PDLong2 (FIG. 4A and B). We observed a significant increase in the number of CD4⁺ T cells that reacted against DCvacc in cultures that had been co-stimulated with both PDLong epitopes compared to those co-stimulated with the control peptide (P=0.008 at baseline and P=0.008 after the fourth vaccination). Hence, CD4⁺ T cell reactivity was increased in all donors at both time points. CD8⁺ T cell reactivity was like-wise significantly increased at baseline (P=0.008) and after the fourth vaccination (P=0.055) in all but one donor.

Mann-Whitney tests revealed that PD-L1 co-stimulation had a significant effect on T cell response when we compared all cultures stimulated with either one or two PD-L1 epitopes to cultures incubated with control peptide. CD4⁺ T cell response: P=0.012 at base line, P=0.002 after fourth vaccination, and P=0.095 after sixth vaccination. CD8⁺ T cell response: P=0.01 at baseline, P=0.076 after fourth vaccination, and P=0.31 after sixth vaccination.

Co-Stimulation with PD-L1 Epitopes Induces IL-6 Production

To examine changes in the cytokine regulatory environment, we used BD™ Cytometric Bead Array (CBA) Flex Set assays to compare cytokine secretion in the supernatants of cultures of PBMCs from four donors. PBMC cultures co-stimulated with the PDLong epitopes showed higher concentrations of proinflammatory cytokines INFγ and IL6 compared to control cultures. Higher IFNγ0 levels compared to control cultures were observed in cultures from three out of four patients at baseline and after the fourth vaccination (FIG. 5A). In addition, a large increase in IL-6 levels was observed in all four patients after co-stimulation with both PDLong peptides (Long 1+2) compared to incubation with control peptide at both time points (FIG. 5B). We also observed lower levels of the regulatory cytokine TGFβ in cultures co-stimulated with both PDLong peptides compared to controls (FIG. 5C). These lower levels of TGFγ were seen in PBMC cultures from two out of four patients at baseline and all four patients after the fourth vaccination/co-stimulation. Other cytokines were measured, such as TNFα, IL10, and IL17, but they could not be detected in any of the supernatants examined (data not shown). In addition to changes in the cytokine profile, cell numbers were higher in most cultures co-stimulated with the PD-L1 epitopes compared to control cultures (FIG. 5D). The increased numbers of cells were observed in cultures from three out of four patients at baseline and from all four patients after the fourth stimulation.

Discussion

Several potential therapeutic strategies that target immunosuppression in cancer are currently under investigation, such as the blocking of inhibitory pathways with monoclonal antibodies.¹⁹ An alternative strategy, which we have adopted, is to utilize specific T cells to target immune suppression.²⁰ In the present study, when we examined the effect on immunogenicity of co-stimulating a DC-based vaccine with long peptide epitopes derived from PD-L1, we found that T cell reactivity toward the vaccine was significantly increased. Reactivity of CD4⁺ T cells increased the most, but CD8⁺ T cell reactivity was also significantly boosted by co-stimulation.

In general, we only observed no or very limited reactivity towards DCvacc in PBMC from patients ex vivo (Borch et al., in preparation). Hence, there was only limited induction of T cell frequencies in vivo in patients vaccinated with DCvacc. This may have been due to the presence of different immunosuppressive mechanisms that may even be boosted by the DCs. Regulatory feedback mechanisms, such as upregulation of PD-L1, are essential in order to limit the intensity and extent of immune responses, which might otherwise cause harm to the host. However, this immune evasion is detrimental within the context of cancer immunotherapy. Thus, the targeting of one or more immunosuppressive pathways may be useful in combination with anticancer immunotherapy in cases where immunosuppressive mechanisms may suppress the effects of therapy.

The results of the present study suggest that the addition of PD-L1 epitopes to a cancer vaccine could strengthen immune responses against the vaccine in vivo. These measures may boost effector T cells by coactivation of proinflammatory PD-L1-specific T cells, which are attracted to the tumor microenvironment due to local expression of PD-L1. Previous studies have reported that exposure of regulatory T cells (Tregs) to IL-6 and other proinflammatory cytokines induces reprogramming of mature Tregs to acquire a phenotype resembling proinflammatory Th17 cells.²¹⁻²³ In the present study, IL-6 levels were significantly higher in cultures that had been co-stimulated with PD-L1 epitopes. Hence, PD-L1-specific T cells may effectively boost the effector phase of the immune response by both direct and indirect release of proinflammatory cytokines, as well as by direct removal of PD-L1-expressing regulatory immune cells that inhibit PD-1-positive T cells. In addition to directly restraining the immune-regulatory effects of PD-L1, PD-L1-specific T cells may inhibit other routes of immune suppression mediated by their cognate target cells.

Early successes in blocking the PD-1 pathway have resulted in commercial interest and competition among drug companies to develop monoclonal antibodies targeting PD-1 or PD-L1. Combined PD-1 pathway blockade with vaccination is a promising alternative approach, as vaccines have been shown to recruit immune effector cells into the tumor microenvironment. Targeting immune regulation by induction of PD-L1-specific T cells is an attractive option to boost the immunogenicity of immunotherapeutic agents, as boosting PD-L1-specific T cells may directly modulate immune regulation and alter tolerance. The combination of vaccination with PD-1 pathway blockade should be easily implementable and synergistic, since PD-L1 blockade by antibodies would make the PD-L1-expressing target cells more vulnerable targets for vaccine-induced T cells. Future investigations are required to confirm the safety, tolerability, and effectiveness of a regimen that includes co-stimulation of PD-L1-specific T cells with PD-L1-derived epitopes.

Example 2 Spontanous Immune Responses Against IO104.1 in Human Patients

We first analysed the immune responses against two versions of IO104.1 in Tumor infiltrating T cells from melanoma patients. Next we analysed if PDL111 specific T cells were able to recognize IO104.1

Materials and Methods Peptides

(minimal epitope - SEQ ID NO: 92) PDL111 = CLGVALTFI (SEQ ID NO: 92) IO104 (PDLong2) = VILGAILLCLGVALTFIFRLRKG (SEQ ID NO: 52) IO104.1-OH = Arg-Thr-His-Leu-Val-Ile-Leu-Gly-Ala- Ile-Leu-Leu-Cys-Leu-Gly-Val-Ala-Leu-Thr-Phe-Ile- Phe-Arg-Leu-Arg-Lys-Gly-Arg-OH (C-terminus acid) (SEQ ID NO: 52 with C terminal amide) IO104.1-NH₂ = Arg-Thr-His-Leu-Val-Ile-Leu-Gly-Ala- Ile-Leu-Leu-Cys-Leu-Gly-Val-Ala-Leu-Thr-Phe-Ile- Phe-Arg-Leu-Arg-Lys-Gly-Arg-NH2 (C-terminus amide)

ELISPOT Assay

The ELISPOT technique enabled screening a high number of peptide antigens for T-cell recognition, despite the availability of relatively few T-cells. We used the ELISPOT assay to quantify peptide-specific, effector cells that secreted IFN-γ, as described in Example 1. We performed the assays according to the guidelines provided by the cancer immunotherapy immunoguiding program (CIP; http://cimt.eu/cimt/files/dl/cip_guidelines.pdf). To measure T-cell reactivity, nitrocellulose-bottomed 96-well plates (MultiScreen MSIPN4W; Millipore) were coated overnight with the relevant antibodies. The wells were washed and blocked with X-vivo medium for 2 h. The Tumor Infiltrating Lymphoctyes (TILs) were added at different cell concentrations in triplicate wells, with PD-L1 peptides or with control peptide, and incubated overnight. The following day, the wells were washed, and the relevant biotinylated secondary antibody (Mabtech) was added, followed by the avidin-enzyme conjugate (AP-Avidin; Calbiochem/Invitrogen Life Technologies); finally, we added the enzyme substrate, NBT/BCIP (Invitrogen Life Technologies) for visualization. The spots on the developed ELISPOT plates were analyzed on a CTL ImmunoSpot S6 Ultimate-V analyzer with Immunospot software, v5.1.

Results

We used the IFNγ ELISPOT assay to examine tumor-infiltrating lymphocytes from 7 melanoma patients for T cell reactivity against IO104.1 peptides. The IFNγ ELISPOT assay revealed a T cell response in tumor-infiltrating lymphocytes cultured with IO104.1 peptides from three of the patients. See FIG. 6.

Next, we examined if CD8 T-cells specific for the minimal epitope CL G V A L T F I (PDL111—SEQ ID NO: 92, which is located within IO104.1) were able to recognize both versions of IO104.1 by ELISPOT. We analysed the reactivity towards PDL111, PDL1₂₄₂₋₂₆₄ (VILGAILLCLGVALTFIFRLRKG-PDLong2, SEQ ID NO: 91), IO104.1 (—OH) and IO104.1 (NH). The T cells were able to react toward both versions of IO104.1. See FIG. 7.

Conclusion

IO104.1 specific T cells are naturally present among tumor infiltrating lymphocytes (TILs) of human melanoma patients. IO104.1 peptides are also recognized by CD8+ T cells specific for a known epitope of PD-L1 which is comprised within the sequence of IO104.1.

Example 3 PDL1 Specific T Cells are Naturally Occurring in Mice

We hypothesized that if PD-L1 specific T cells are natural occurring, they should activate and expand in response to inflammation.

Materials and Methods

C56BL/6 mice were injected with 1 μg IFNγ in 200 μl PBS i.p (or no injection for control) two days apart (day 0+2) to simulate inflammation. On day 5 the mice were sacrificed and a single cell solution of the removed spleen was made for further analysis by IFNγ-Elispot.

9×10⁵ splenocytes/well were stimulated ex vivo in Elispot plates with 5 μg/ml peptides from murine (m)PDL1 for 18-20 hours. Spot count for the peptide stimulated wells was subtracted the background (spot count of wells with no peptide stimulation).

The peptides from PDL1 were selected based on the following reasoning.

The Sequence of mPD-L1 is:

(SEQ ID NO: 95 - N-terminal/signal sequence in bold, C-terminal/membrane-spanning region underlined) MRIFAGIIFT ACCHLLRAFT ITAPKDLYVV EYGSNVTME CRFPVERELD LLALVVYWE KEDEQVIQFV AGEEDLKPQH SNFRGRASLP KDQLLKGNA ALQITDVKLQ DAGVYCCII SYGGADYKRI TLKVNAPYRK INQRISVDPA TSEHELICQ AEGYPEAEVI WTNSDHQPV SGKRSVTTSR TEGMLLNVTS SLRVNATAND VFYCTFWRS QPGQNHTAEL IIPELPATH PPQNRTHWVL LGSILLFLIV VSTVLLFLRK QVRMLDVEK CGVEDTSSKN RNDTQFEET

This sequence is significantly different to that of human (h)PDL1, so it is not possible to use the same peptides for testing in mice as in humans. However, we deliberately selected peptides from the regions of mPDL1 which correspond approximately to those regions in hPDL1 from which the sequences of PDlong1 and PDlong2 are derived (see Examples 1 and 2). That is, from the N terminal/signal sequence and the C terminal/membrane-spanning region of mPDL1.

The following peptides were chosen:

(mLong1; SEQ ID NO: 96) MRIFAGIIFTACCHLLRA (mLong2; SEQ ID NO: 97) FTACCHLLRAFTITAPKDL (mLong3; SEQ ID NO: 98) WVLLGSILLFLIVVSTVLLFLRKQV (mLong4; SEQ ID NO: 99) TVLLFLRKQVRMLDVEKCGV (mLong5; SEQ ID NO: 100) MLDVEKCGVEDTSSKNRNDTQFEET

mLong1 and 2 are overlapping sequences from the region of mPDL1 shown in bold above; mLong3, 4 and 5 are overlapping sequences from the region of mPDL1 shown underlined above. mLong1 is considered to be the closest mouse equivalent to the human peptide of PDlong1. mLong3 is considered to be the closest mouse equivalent to the human peptide of PDlong2.

Results and Conclusion

Result of the Elispot are shown in FIG. 8. All 5 murine peptides were recognized by T cells following the prior stimulation with IFNγ, thus indicating that T cells specific for epitopes within these sequences are naturally present in mice even without vaccination. The most positive results were obtained with mLong1 and mLong3. In subsequent murine experiments, for simplicity only mLong1 was used, but similar results would be expected with at least mLong3.

Example 4

Further Support for Naturally-Occurring PDL1 Specific T Cells in Mice

Given the result in Example 3, we hypothesized PD-L1 specific T cells should also activate and expand in response to local stimulation, such as the inflammatory response to an allergen.

Materials and methods

A solution of 0.15% 2,4-dinitrofluorobenzene (DNFB; an allergen) in 1:4 olive oil/acetone (OOA) (or just OOA as a control) was painted on back of both ears of C56BL/6 mice for 3 consecutive days (days 0-2). On day 5 the mice were sacrificed and a single cell solution of the removed spleen and draining lymph nodes (dLNs) was made for further analysis by IFNy-Elispot.

8-9×10⁵ cells/well were stimulated ex vivo in Elispot plates with 5 μg/ml mPD-L1long1 (mLong1 from Example 3) or mPD-L1short (a part of the mLong1 peptide having the sequence GIIFTACCHL (SEQ ID NO: 101)) for 18-20 hours. Spot count for the peptide stimulated wells was subtracted the background (spot count of wells with no peptide stimulation).

Results and Conclusion

Results of the Elispot are shown in FIG. 9. Splenocytes and dLNs recognized both the long and short peptides in mice treated with DNFB, but not with control, confirming that naturally-occurring PDL1 specific T cells do indeed activate and expand in response to local allergen stimulation. The responses to both long and short peptides shows that the response is likely due to both CD8+ and CD4+ T cells. The short peptide should only be bound and presented by MHC class I and hence can only stimulate CD8+ T cells. The long peptide will (after processing) potentially be bound and presented by MHC class I and II, hence stimulating both CD8+ and CD4+T cells.

Example 5 PDL1-Specific Responses in Mice are Increased by Vaccination with PDL1 Peptides Materials and Methods

C56BL/6 mice were vaccinated subcutaneously (s.c) on the lower back with 100 μg mPD-L1long1 (mLong1 from Example 3) with or without Montanide as an adjuvant (only Montanide as a control) at day 0. On day 7 the mice were sacrificed and a single cell solution of the removed spleen was made for further analysis by IFNy-Elispot.

9×10⁵ splenocytes/well were stimulated ex vivo in Elispot plates with 5 μg/ml mPD-L1long1 or mPD-L1short for 18-20 hours. Spot count for the peptide stimulated wells was subtracted the background (spot count of wells with no peptide stimulation).

Results and Conclusion

Results of the Elispot are shown in FIG. 10. A strong PD-L1-specific T cell response was seen in the spleens and draining lymph nodes (DLNs) of the peptide-vaccinated mice compared to mice vaccinated with the adjuvant alone. Ex vivo stimulation with both mPD-L1long and the shorter version mPD-L1short showed increased PD-L1-specific response in mPD-L1 long vaccinated mice seen by IFNy Elispot.

Example 6 Vaccination with mPD-L1long1 shows anti-tumor effect in mice Materials and Methods

C56BL/6 mice were inoculated with 2×10⁵ B16F10 tumor cells subcutaneously (s.c) on one side of lower back (day 0). The tumor cells were pre-stimulated with IFNy in vitro for 24h before inoculation. At day 0 and day 7 mice were vaccinated s.c on the other side of lower back with 100 μg mPD-L1long1 with Montanide as an adjuvant (only Montanide as a control). Tumor size was measured 3x/week and mice were sacrificed when tumors got too big.

Results and Conclusion

Results are shown in FIG. 11. The mice vaccinated with peptide+montanide showed reduced tumor growth and better survival than mice vaccinated with montanide only. Thus anti-PDL1 T cells expanded and activated by the vaccination have an anti-tumoral effect.

Overall Conclusion for Examples 3 to 7 (in vivo testing)

We describe that PD-L1 specific T cells are expanded by IFNy injections (Example 3) and local stimulation with allergens (Example 4), which suggests that PD-L1 specific T cells are already present and are activated and proliferate upon receipt of a strong activation signal from their cognate targets (i.e. professional antigen-presenting cells) at inflammation sites. We demonstrate that PD-L1 specific T cells are easily expanded by vaccination and that an anti-tumoral effect results. Thus, PD-L1-specific T cells are a particularly interesting example of the immune system's ability to influence adaptive immune responses by directly reacting against the immune-suppressive mechanisms employed by cancerous cells. Vaccination using PDL1 peptides has been shown to have a direct benefit in vivo.

General Details for Elispot Methodology

-   -   Following sacrifice of mice, spleen (and draining lymph nodes         (dLNs)) were removed.     -   Spleen and dLNs was smashed through a 70 μM cell strainer into a         50 ml tube with media (RPMI+10% FCS +1% pen/strep) and washed         for at 300 G for 5 minutes, repeated for dLNs. Splenocytes was         lysed with RBC lysis buffer for 1 min and washed in media twice.     -   Cells were counted and transfered to IFNy Ab-coated Elispot         plates in cell number of 9×10⁵ cells/well. Coating antibody:         Anti-mouse IFN-g mAb AN18 (Mabtech cat no. 3321-3-1000).     -   Stimulatory peptides were added to designated wells in         concentrations of 5 μg/ml. Control wells were not stimulated         with peptide.     -   Elispot plates were developed after 18-20 hours.     -   Detection antibody Anti-mouse IFN-g mAb R4-6A2-Biotin (Mabtech         cat no. 3321-6-1000). Avidin-enzyme conjugate (AP-Avidin;         Calbiochem/Invitrogen Life Technologies) and enzyme substrate,         NBT/BCIP (Invitrogen Life Technologies) used for visualization.     -   Spot count for peptide-stimulated wells was always subtracted         the corresponding wells without peptide stimulation (the         background)     -   Negative values were sat to zero.

Full length sequence of human PD-L1 (SEQ ID NO. 1) Met Arg Ile Phe Ala Val Phe Ile Phe Met Thr Tyr 1               5                   10 Trp His Leu Leu Asn Ala Phe Thr Val Thr Val Pro         15                  20 Lys Asp Leu Tyr Val Val Glu Tyr Gly Ser Asn Met 25                  30                  35 Thr Ile Glu Cys Lys Phe Pro Val Glu Lys Gln Leu             40                  45 Asp Leu Ala Ala Leu Ile Val Tyr Trp Glu Met Glu     50                  55                  60 Asp Lys Asn Ile Ile Gln Phe Val His Gly Glu Glu                 65                  70 Asp Leu Lys Val Gln His Ser Ser Tyr Arg Gln Arg         75                  80 Ala Arg Leu Leu Lys Asp Gln Leu Ser Leu Gly Asn 85                  90                  95 Ala Ala Leu Gln Ile Thr Asp Val Lys Leu Gln Asp             100                 105 Ala Gly Val Tyr Arg Cys Met Ile Ser Tyr Gly Gly     110                 115                 120 Ala Asp Tyr Lys Arg Ile Thr Val Lys Val Asn Ala                 125                 130 Pro Tyr Asn Lys Ile Asn Gln Arg Ile Leu Val Val         135                 140 Asp Pro Val Thr Ser Glu His Glu Leu Thr Cys Gln 145                 150                 155 Ala Glu Gly Tyr Pro Lys Ala Glu Val Ile Trp Thr             160                 165 Ser Ser Asp His Gln Val Leu Ser Gly Lys Thr Thr     170                 175                 180 Thr Thr Asn Ser Lys Arg Glu Glu Lys Leu Phe Asn                 185                 190 Val Thr Ser Thr Leu Arg Ile Asn Thr Thr Thr Asn         195                 200 Glu Ile Phe Tyr Cys Thr Phe Arg Arg Leu Asp Pro 205                 210                 215 Glu Glu Asn His Thr Ala Glu Leu Val Ile Pro Glu             220                 225 Leu Pro Leu Ala His Pro Pro Asn Glu Arg Thr His     230                 235                 240 Leu Val Ile Leu Gly Ala Ile Leu Leu Cys Leu Gly                 245                 250 Val Ala Leu Thr Phe Ile Phe Arg Leu Arg Lys Gly         255                 260 Arg Met Met Asp Val Lys Lys Cys Gly Ile Gln Asp 265                 270                 275 Thr Asn Ser Lys Lys Gln Ser Asp Thr His Leu Glu             280                 285 Glu Thr     290

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1-17. (canceled)
 18. A PD-L1 peptide fragment, or a pharmaceutically acceptable salt thereof, having the formula: X¹VILGAILLCLGVALTFIX²

wherein N-terminal X¹ is selected from a group consisting of L, HL, THL, RTHL (SEQ ID NO: 79), ERTHL (SEQ ID NO: 80), NERTHL (SEQ ID NO: 81), or is absent, C-terminal X² is selected from a group consisting of F, FR, FRL, FRLR (SEQ ID NO: 82), FRLRK (SEQ ID NO: 83), FRLRKG (SEQ ID NO: 84), FRLRKGR (SEQ ID NO: 85), FRLRKGRM (SEQ ID NO: 86), FRLRKGRMM (SEQ ID NO: 87), FRLRKGRMMD (SEQ ID NO: 88), or is absent, provided that if X¹ is absent then X² is not FRLRKG (SEQ ID NO: 84), and provided that if X¹ is NERTHL (SEQ ID NO: 81) then X² is not FRLR (SEQ ID NO: 82), wherein the C-terminal amino acid may also comprise the amide.
 19. The peptide fragment of claim 18, wherein the peptide fragment has the amino acid sequence of RTHLVILGAILLCLGVALTFIFRLRKGR (SEQ ID NO: 52) including a C terminal amino acid or amide.
 20. The peptide fragment of claim 18, wherein the peptide fragment is selected from the group consisting of: NERTHLVILGAILLCLGVALTFIFRLRKGRMMD-OH (SEQ ID NO: 77); NERTHLVILGAILLCLGVALTFIFRLRKGRMMD-NH₂ (SEQ ID NO: 77 with C terminal amide); RTHLVILGAILLCLGVALTFIFRLRKGR-OH (SEQ ID NO: 52); RTHLVILGAILLCLGVALTFIFRLRKGR-NH₂ (SEQ ID NO: 52 with C terminal amide); NERTHLVILGAILLCLGVALTFI-OH (SEQ ID NO: 67); NERTHLVILGAILLCLGVALTFI-NH₂ (SEQ ID NO: 67 with C terminal amide); VILGAILLCLGVALTFI-OH (SEQ ID NO: 2); and VILGAILLCLGVALTFI-NH₂ (SEQ ID NO: 2 with C terminal amide), or a pharmaceutically acceptable salt thereof.
 21. The peptide fragment of claim 18, wherein the peptide fragment is selected from the group consisting of: NERTHLVILGAILLCLGVALTFIFRLRKGRMMD-OH (SEQ ID NO: 77); RTHLVILGAILLCLGVALTFIFRLRKGR-OH (SEQ ID NO: 52); and RTHLVILGAILLCLGVALTFIFRLRKGR-NH₂ (SEQ ID NO: 52 with C terminal amide).
 22. A composition comprising the PD-L1 peptide fragment of claim
 18. 23. The composition of claim 22, further comprising one or more of a pharmaceutically acceptable additive, a preservative, and an adjuvant.
 24. The composition of claim 23, wherein the adjuvant is selected from the group consisting of bacterial DNA based adjuvants, oil/surfactant based adjuvants, viral dsRNA based adjuvants, imidazochinilines, and a Montanide ISA adjuvant.
 25. A method of treating a clinical condition characterized by expression of PD-L1, the method comprising administering to an individual suffering from said clinical condition an effective amount of: the peptide fragment of claim 18; or a PD-L1 peptide fragment having the formula: FMTYWHLLNAFTVTVPKDL (SEQ ID NO: 89) wherein the C-terminal amino acid also comprises the amide, or a pharmaceutically acceptable salt.
 26. The method of claim 25, wherein the clinical condition is a cancer where PD-L1 is expressed.
 27. The method of claim 26, wherein the cancer is a tumor.
 28. The method of claim 25, wherein the clinical condition is an infectious disease, e.g. an intracellular infection, for example an intracellular infection with a pathogen selected from the group consisting of L. monocytogenes and plasmodium, or a viral infection, for example an infection with a virus selected from the group consisting of HIV and hepatitis.
 29. The method of claim 25, wherein the clinical condition is an autoimmune disease, such as diabetes, SLE and sclerosis.
 30. The method of claim 25, further comprising simultaneously or sequentially administering to the individual an effective amount of an additional cancer therapy.
 31. The method of claim 30, wherein the additional cancer therapy is a cytokine therapy, a T-cell therapy, an NK therapy, an immune system checkpoint inhibitor, chemotherapy, radiotherapy, immunostimulating substances, gene therapy, antibodies and/or dendritic cells.
 32. The method of claim 30, wherein the additional cancer therapy is selected from the group consisting of Actimide, Azacitidine, Azathioprine, Bleomycin, Carboplatin, Capecitabine, Cisplatin, Chlorambucil, Cyclophosphamide, Cytarabine, Daunorubicin, Docetaxel, Doxifluridine, Doxorubicin, Epirubicin, Etoposide, Fludarabine, Fluorouracil, Gemcitabine, Hydroxyurea, Idarubicin, Irinotecan, Lenalidomide, Leucovorin, Mechlorethamine, Melphalan, Mercaptopurine, Methotrexate, Mitoxantrone, Nivolumab, Oxaliplatin, Paclitaxel, Pembrolizumab, Pemetrexed, Revlimid, Temozolomide, Teniposide, Thioguanine, Valrubicin, Vinblastine, Vincristine, Vindesine and Vinorelbine.
 33. A kit-of parts comprising: a) the composition of claim 22, and b) a composition comprising at least one second active ingredient, wherein the second active ingredient is selected from the group consisting of an immunostimulating compound e.g. IL-2 and/or IL-21, and an anti-cancer agent e.g. Actimide, Azacitidine, Azathioprine, Bleomycin, Carboplatin, Capecitabine, Cisplatin, Chlorambucil, Cyclophosphamide, Cytarabine, Daunorubicin, Docetaxel, Doxifluridine, Doxorubicin, Epirubicin, Etoposide, Fludarabine, Fluorouracil, Gemcitabine, Hydroxyurea, Idarubicin, Irinotecan, Lenalidomide, Leucovorin, Mechlorethamine, Melphalan, Mercaptopurine, Methotrexate, Mitoxantrone, nivolumab, Oxaliplatin, Paclitaxel, pembrolizumab, Pemetrexed, Revlimid, Temozolomide, Teniposide, Thioguanine, Valrubicin, Vinblastine, Vincristine, Vindesine and Vinorelbine.
 34. The kits-of-parts of claim 33, wherein the provided compositions are to be administered simultaneously or sequentially. 